It's sort of been replaced by mobile apps, but there's still a lot of Flash out there. Kongregate is still a thing. Browser-based games are currently in this weird limbo state where the old tech is out of favor, but the new hotness (WebGL) really isn't ready yet.
The WebGL exports you currently get from Unity and UE4 are typically huge, slow, and often completely broken. I have no idea where the blame lies, but it's not pretty.
Do you actually play on Kongregate? I check it on occasion and have noticed that it hasn't really changed over the last five years. 90% of the games I see at a glance aren't any different.