entertaining

It's old as hell, Half Life 2's weapons do not work well in a PVP game and the time to kill is way too high but maaaaan, this is some stupid fun.
It gives a me a nice feeling reminding me of old school Steam times around 2008-2009 when PVP games were more simple and playing janky Source mods.

You can kill people with a toilet.

I don't really understand why they unlisted this for Half-Life 2's 20th. I almost wondered if the actual Half-Life 2 client would've received deathmatch or multiplayer integration, but at a glance it seems like that isn't the case.

I personally still think this is worth playing today. Finding matches in older arena shooter games might sometimes require some coordination outside of the server browser itself but if you're the type to go looking for that then I would recommend this.

Edit: Some of these 20th anniversary bug fixes don't seem to actually have been implemented. Supposedly this also broke the game on linux? I hope this is temporary.