Meanwhile, my wife got me an "official" Tetris handheld game for Christmas and not only does it only have 15 levels, but the music repeats once and then stops until you restart the game.
You know what I would love? A basic, no-frills Tetris game for my phone. I don't know why that is too much to ask for.
I appreciate the advice and I'll definitely look into it, but I really shouldn't have to look into it or run an emulator. If the company that owns Teris (who now sue anyone trying to put out a similar game) just put out a simple version of Tetris with an ad banner at the bottom, they would make serious bank from all of us older people who grew up playing it constantly. They would probably even make a decent amount of money if they charged for it up front.
There is an official Tetris phone game. It's shit. There's no normal Tetris mode on it. I really don't understand.
You can also get cheap, ESP32 based gameboy pocket style emulator handhelds that are nice. They stopped making the original Odroid Go, but there are others out there.
Check out falling lightblocks. I'm not sure if it's on iPhone but on Android you have to get it from their website because Google removed it from the playstore because they got copyright claimed
Blame the Tetris Guideline. In the mid 2000s, they changed the rotation system, and under the new system, any player of intermediate skill can just play forever. Once you know the tricks to keeping a piece in play and building the stack in a way that you can always get a piece where you want it, you can't lose until you voluntarily lose. That was, needless to say, a bit broken for leaderboard purposes. So as a bandaid solution to that, the main mode was changed from endless to 150 lines.
The difficulty curve in Tetris has a few different possible knobs to adjust as the levels go up, generally involving how much of a delay you have on certain events. The most obvious is gravity, which is how many frames it takes to fall one space (or, to ramp that up further, how many spaces it falls per frame), but the relevant one here is lock delay. This is the amount of time between the piece landing and the player losing control over the piece. Low lock delay like you have on NES tends to make small mistakes a lot more punishing. High lock delay lets you reposition a piece shortly after it falls. Modern Tetris has a small but highly controversial change to the lock delay logic: rotating a piece resets the timer. This means you can spam the rotate button to think about where to place a piece indefinitely, a technique called infinite spin. Presumably this was done with timed and battle modes in mind, where this isn't really an advantage because it's always better to play quickly, but in endless it has no meaningful cost. So leaderboards started to get pretty grotesque, with top scoring games dragging on for dozens of hours. Something had to be done about it, and shifting focus entirely to timed and line limited modes was the choice they made for better or worse.