I mean, those sites still exist, but it's a different culture of game dev now. People passionate enough to make interesting, free games aren't attracted to the 'mass free flash game' style website.
Armorgames is still online, though who knows what kind of strange things you might find on there. Probably a lot of rehashed concepts. There's a lot of free games on mobile now, too, and I'm guessing it has a much larger share of game dev than desktop these days, at least for the category of 'simple but entertaining' style games. I figure anyone with a desktop has their choice of unique and investment-worthy AAA titles, or high-production quality indie.
Honestly, good riddance. The space has opened up greatly for people to create interesting things, and I cringe thinking of all the time I wasted on random tower defense games that were all kind of the same at the end of the day.
If you want, check out Alpha Beta Gamer, kind of a game-announcement blog. I would start with the oldest archived post and work your way forward. They post more than just free games, sometimes paid-for ad articles, but honestly after Rock Paper Shotgun went the way of PCGamer and became veeeery uninteresting, it's the last place I know that posts about all sorts of weird unity-demo, student project type games. You know, the games that never get finished but are so entertaining as a proof of concept you still have a folder full of them years later. Alpha Beta also has a youtube channel now where they do pretty extensive playthroughs so you can get a good idea if you want to give the game a try.
What a weird time that was, eh? The era of flash. Still think about Newgrounds occasionally. It's a trip to go through the top-rated playlist now, and see what things were THE BEST back then. The animations, the games. . it's enough to take one back to their younger days.