The Single Player is amazing, this review is indicative of Red Dead Online.
As someone with over 2700 hours this is my final verdict.

Oh boy! Bounty hunter! Posse gets hyped to do a bounty, ya'll show up, kill a solid 2-3 guys each, one ties em up, you're done. 12 minutes remaining. A few measly enemies following you. Posse member: "iF yOu SiT aNd wAiT tHe TiMeR oUt YoU gEt PaId MoRe". I don't want to wait, I want to do stuff and get paid to do it.
Bounty hunter again, everyone goes to the location, search for 5 minutes for a single guy taking a leak on a tree.
Steal a wagon from a convoy of guys? Bring it back to your camp, or your contractor for a measly couple bucks.
Do a free roam mission? Deliver the mail? Steal the wagon? RIVAL PLAYERS CAN STEAL YOUR MISSION. Get ready for anything. Realize the game put you in a solo session.
Woohoo, Trader! Hunting is cool, hunt stuff, deliver stuff, run wagons and be ready for an attack, nothing, or steal a trader wagon from a player only for them to leave, yell at you for playing the game, then leave, or you actually fight them, thank goodness, Yay! Excitement! No real reward for stealing though. Get materials lol.
Naturalist. go to harriet, get sprayed, leave, forget naturalist for a sec, kill some animals, remember naturalist, get sprayed.
Moonshiner! Upfront cost is wild, tell yourself the return is worth it, run your moonshine, run over a pebble, break a bottle, 50% of value lost. Moonshiner revenue agent camps replace gang hideout spawns. Broken sabotage/poison the batch missions. Only 5 total moonshine story missions. 2 are broken. (Moonshine shack with your friends is cool though)
King of the Castle! No one plays objective, or a Modder does.
Dispatch Rider. Whole lobby leaves and stops trying, get $10 for winning.
Railroad Baron. two good players actually fighting to get on the train, the rest of the lobby complaining in voice chat they're stuck in spawn when they're just staying in spawn, killing each other
Horseback kills challenge. Everyone is shooting each other. Kill a few players horses on accident. Get charged $16. Make only $10. Leave at a loss, even though you won.
Horse races, dead lobby.
Showdowns, dead lobby. (You can't host a match so no one ever searches at the same time)
Treasure maps, broken pickups.
Blood money Capitale missions! ♥♥♥♥ yeah. Try to get capitale, Find no capitale, realize there really just isn't much at all in the missions, realize that capitale is just crapitale, finally save some crapitale, do 1 of only 3 repetitive "Opportunities" you can complete in literally 5 minutes if you wanted to, sit and farm it hoping to get a bunch of money, get less money than a 1 star legendary bounty.
Story missions in Online? Sounds promising. Play them, realize it ends on an unfinished cliffhanger. Think to yourself the missions were kinda good though. Go to play them again. Make $13.
Collector, broken pickups, items missing, get to Madam Nazar, Processing Transaction...
Player bounty, accept it, nothing happens, "huh? guess it didn't start" It starts, 1:30 remaining.
Working player bounty, player stands there, player leaves.
Killing a bunch of cops and get a bounty! disruptive, discourages you from doing so with either starting a "Mission" to "Kill the bounty hunters" instead of it being like a wanted level, or having a bounty above $10 locks you out of most content.
A new horse, his tail is gone, his mane is gone, his head is stuck sideways, realize this is a game breaking bug that's been in the game for a year.
Sweet, a vehicles section! I can buy and own my own wagon? Wagon customization? No. Bounty Wagon, Hunting Wagon, only usable on roads. Inconvenient.
New outlaw pass! New outlaw pass?
Modders, modders everywhere. Peer to peer exploits, being able to literally close your game if they want to. Session following, teleporting, ruining PvP with invincibility and anything else they are around.
Mexico is literally in the game, you can see it, you can glitch out there and go to it, realize they're never adding mexico or updating the game again.

Play single player, don't touch Online.

The Single Player is amazing, this review is indicative of Red Dead Online. As someone with over 2700 hours this is my final verdict. Oh boy! Bounty hunter! Posse gets hyped to do a bounty, ya'll show up, kill a solid 2-3 guys each, one ties em up, you're done. 12 minutes remaining. A few measly enemies following you. Posse member: "iF yOu SiT aNd wAiT tHe TiMeR oUt YoU gEt PaId MoRe". I don't want to wait, I want to do stuff and get paid to do it. Bounty hunter again, everyone goes to the location, search for 5 minutes for a single guy taking a leak on a tree. Steal a wagon from a convoy of guys? Bring it back to your camp, or your contractor for a measly couple bucks. Do a free roam mission? Deliver the mail? Steal the wagon? RIVAL PLAYERS CAN STEAL YOUR MISSION. Get ready for anything. Realize the game put you in a solo session. Woohoo, Trader! Hunting is cool, hunt stuff, deliver stuff, run wagons and be ready for an attack, nothing, or steal a trader wagon from a player only for them to leave, yell at you for playing the game, then leave, or you actually fight them, thank goodness, Yay! Excitement! No real reward for stealing though. Get materials lol. Naturalist. go to harriet, get sprayed, leave, forget naturalist for a sec, kill some animals, remember naturalist, get sprayed. Moonshiner! Upfront cost is wild, tell yourself the return is worth it, run your moonshine, run over a pebble, break a bottle, 50% of value lost. Moonshiner revenue agent camps replace gang hideout spawns. Broken sabotage/poison the batch missions. Only 5 total moonshine story missions. 2 are broken. (Moonshine shack with your friends is cool though) King of the Castle! No one plays objective, or a Modder does. Dispatch Rider. Whole lobby leaves and stops trying, get $10 for winning. Railroad Baron. two good players actually fighting to get on the train, the rest of the lobby complaining in voice chat they're stuck in spawn when they're just staying in spawn, killing each other Horseback kills challenge. Everyone is shooting each other. Kill a few players horses on accident. Get charged $16. Make only $10. Leave at a loss, even though you won. Horse races, dead lobby. Showdowns, dead lobby. (You can't host a match so no one ever searches at the same time) Treasure maps, broken pickups. Blood money Capitale missions! Fuck yeah. Try to get capitale, Find no capitale, realize there really just isn't much at all in the missions, realize that capitale is just crapitale, finally save some crapitale, do 1 of only 3 repetitive "Opportunities" you can complete in literally 5 minutes if you wanted to, sit and farm it hoping to get a bunch of money, get less money than a 1 star legendary bounty. Story missions in Online? Sounds promising. Play them, realize it ends on an unfinished cliffhanger. Think to yourself the missions were kinda good though. Go to play them again. Make $13. Collector, broken pickups, items missing, get to Madam Nazar, Processing Transaction... Player bounty, accept it, nothing happens, "huh? guess it didn't start" It starts, 1:30 remaining. Working player bounty, player stands there, player leaves. Killing a bunch of cops and get a bounty! disruptive, discourages you from doing so with either starting a "Mission" to "Kill the bounty hunters" instead of it being like a wanted level, or having a bounty above $10 locks you out of most content. A new horse, his tail is gone, his mane is gone, his head is stuck sideways, realize this is a game breaking bug that's been in the game for a year. Sweet, a vehicles section! I can buy and own my own wagon? Wagon customization? No. Bounty Wagon, Hunting Wagon, only usable on roads. Inconvenient. New outlaw pass! New outlaw pass? Modders, modders everywhere. Peer to peer exploits, being able to literally close your game if they want to. Session following, teleporting, ruining PvP with invincibility and anything else they are around. Mexico is literally in the game, you can see it, you can glitch out there and go to it, realize they're never adding mexico or updating the game again. Play single player, don't touch Online.