I am one of those who still miss Dominion
I played TT a lot in the past just like Dominion. For me those were fun modes because they allowed me to pick and try new champs without the pressure and stress from SR. The games are faster, less serious, people are more forgiving and way less toxic and you can just lay back, relax and enjoy a fun game. The best thing about Dominion was that the balance team never touched it. Ironically Dominion felt way more balanced than SR and would often be my place to go whenever the balance and design team messed something completely up. Dominion was usually unaffected and since the balance quality of SR has gone down a lot for me trough the years, over time I used to spent more time playing Dominion with offmeta builds on offmeta champs etc all kind of things that would never work in SR and have a good time. After the removal of Dominion I started playing more TT until the funneling got too big of a problem. Last year I quit League.
I haven't touched League in almost a year now. SR just isn't what it used to be and the game lacks a gamemode like Dominion where you can just play and do silly things and have a fun time without all the stress and try hard SR requires. Not everyone wants to sit and grind SR all day long, especially people with jobs, family, busy lives. Veteran players who started playing 10-5 years ago are now grownups with different needs but they still enjoy a game of League from time to time. I feel like this group of people have been alienated completely and the stupid thing is, now that we have jobs we have more money to spend.