Removing URF is a huge loss of revenue for Riot
I know for myself, I just can't bring myself to really play anymore. I know others who feel the same way. URF is just so much more satisfying because you don't have to invest in 20 minutes of "trying to get to my power spike" only for your team to feed and then feel like the entire time was wasted because you never even felt impactful.
URF is great because you can be aggressive and crazy or methodical and strategic and still have a satisfying experience. In normal games, one type of player or the other usually misses out. It's really just the same game, except accelerated. And that's great for people who don't prefer to have to reach 50 minutes to have a good game.
I also noticed that there were A LOT of people who either returned to the game or tried it out again after leaving just because of URF. There were a LOT of people who were noticeably behind on the changes and mechanics of newer champions. I know a lot of elitists will say that URF shouldn't be brought back. But if you don't like it, you can play another mode! That's the great thing about having options. I'm pretty sure that you, Riot, know that the amount of players online has significantly decreased.