I think 2010-2017 was my school's flash game phase. I think it started fading away when HTML5 was introduced and flash-less computers with Windows 10 were introduced. I think it stopped completely when Fortnite was released. I have heard many people have nostalgia for a flash games website named "Cool Math Games". (Despite the name, many of its games were not math-related. Possibly so that schools would not block the website >:)) But we never went on Cool Math, instead, Friv was the most popular website.
I myself, preferred A10, as it did not remove a game should it be too unpopular. Even though those websites had differing names from Cool Math, they shared much of the same games. The most popular games were (in no particular order): Fireboy and Watergirl, the Papa's series of games (e.g. Papa's Pizzeria), and Red Ball. I remember playing the game "Stealing the Diamond" when I was a child. I also played the prequels (Breaking the Bank, Escaping the Prison and Infiltrating the Airship) when I was older. There's also a new game called "Fleeing the Complex". I've only played it a little bit.