Puyo Puyo Tetris was the only game I ever bought a non-North-American version of, after watching Giant Bomb play it. As far as I can tell, it never got a real NA version for Xbox, or if it did, I missed it. I didn’t even notice the Steam version of PPT1 until looking it up for this comment. The slowdown problems you experienced may be relegated to the Switch version, because…it’s the Switch.

“…any developer releasing a multiplayer game in this day and age without cross play is making a huge mistake.” They’re the ones who have to pay for it though. You’re talking about a game that you acknowledge as niche, which is even harder to justify additional expenses for. The only entity offering cross play services for free is Epic, and some people, for reasons I don’t understand, will whine about Epic Online Services if the game includes them. Otherwise, it’s an expense out of the developer’s/publisher’s pocket, and in a world without LAN and direct IP connections, that means the online dies when that expense no longer makes financial sense. You may not like playing against bots, but you’d also hate playing against absolutely no one. They’re not the first ones to pull this strategy, and there’s a lot of nuance to it.

As for appeal to bring new players in, I was at Combo Breaker 2022, with a friend of mine. He was watching DBFZ top 24 (IIRC) right next door, and he couldn’t stand the sounds coming from the PuyoPuyo stage, so I’d call that a barrier to getting new players in, too. I don’t know that some new game is going to solve the player acquisition problem without a new gimmick. My recommendation? Make your own PuyoPuyo, like Kirby’s Avalanche, but with blackjack and hookers.