Fair, you definitely become more skilled (I put 500 or so hours into DotA 2 years ago), and you can somewhat measure that, but I find it's not nearly as potent.
My additional issue, if you take a long break like I did, is that the MMR somewhat traps you. When I came back, not only was it extremely frustrating to have the head knowledge about what I needed to do (I.E. denying creeps and stealing last hits for optimal farming) while not having the skill to execute it anymore, but I was also trapped in matches with only players who had the skill to capitalize on those mistakes and destroy me. Add to that the pressure of letting down a whole team of 5 players, and my attempts to get back into the game later were miserable.
By comparison, I'm returning to Celeste right now, and checking out the strawberry jam mod. It's been incredibly satisfying to see how quickly I pick up and relearn those mechanics, and I'm just crushing the base game levels that gave me so much trouble the first time, while giving me an enjoyable de-rust. It's been a pleasure to dive back in, and I'm excited to see what heights I can reach, eager to beat the Farewell DLC that I gave up on before and to push myself to even harder modded content.
Maybe I could get a similar experience in DotA, by playing hours of bot matches to relearn fundamentals, and watching lots of YouTube content to learn how the meta is shifted in my absence, but that's a much different grind than I'm having in Celeste, just enjoying the nostalgia of the game and revelling in how much quicker relearning is than the initial learning. And I never have to cope with any social pressures of letting my team down, or watching my hard earned MMR crumble away as the game repeatedly reminds me how much worse I've gotten.
Yeah, personally I've always enjoyed playing IRL with people who are better than me. Having a real person gives me that constant measuring stick I'm looking for, and playing with someone better gives me someone to watch and learn from, which helps me improve way more quickly. But that's... not what gets you the big sales numbers and a smooth player onboarding.
For PvP stuff, the experience I enjoyed the most was playing Smash with dorm mates in college. Getting my ass handed to me in 1v1 matches for months by the guy who owned the console, but learning, grinding, letting that guy I wanted to beat motivate me to use the training room, to watch YouTube videos, study techniques, and try to really master my character, learning how to be unpredictable and perform mix ups that needed to fool an experienced player who knew my weaknesses better than anyone, it was so satisfying. And by the end of the year we were on even footing, and I was maybe even a little better, which just felt incredible and so well earned.
That experience is what ranked PvP just completely lacks. Every time you win they just swap in new players who are that little step better than you until you're perfectly even again. Which is great on a game-to-game scale, each battle is hard fought, but just offers nothing on that wider timescale that I need to really care.