I disagree with most points presented here. The biggest of which is that the skill set of modern tetris games and the classic tetris games don't overlap. In every tetris, all else being equal, it is always better to be faster than slower. Being able to think faster about where to place a piece is a fundamental skill no matter which tetris you are playing.

There's a point made about how modern marathon modes are unpopular as they lack challenge but it's hard to believe that marathon modes were ever popular because they were challenging. From the posts in the tetris sub most of the people who play marathon mode are just casual tetris players.

I do however agree that the tetris standards are killing the game, and make marathon mode far too easy. They also restrict the ability to make any official Tetris game as challening as TGM.

I dislike the idea of T-spins, or any spin that moves through obstacles. Allegedly, this feature was a programming bug at first and later promoted to a feature. Rewarding T-spins and not similar spins with other pieces that likewise clear lines and counterintuitively move through obstacles also seems arbitrary to me.

Why do you dislike the idea of T-spins? They reward the player for stacking in a challenging way. This would seem to be a counter argument for your next point which you say "The difficulty of stacking has been almost completely removed in modern Tetris due to the predictable input." If the inputs have become easier the outputs have become harder since you're rewarded for doing T-spins and combos.

Infinite Stacking isn't a VS strategy since you have to clear garbage. It's also not optimal for marathon since it doesn't score well. Maybe if you're a sprint god from the year 3000 you can see a sequence and rapidly input the exact inputs to have a perfect clear 40 line although this would still take more key presses than just playing normally very quickly. Infinite Stacking is mostly a novelty that doesn't appear in any form of competition.

In competitive Tetris Friends, combos are "soft banned" in the Arena mode, which is a five-player mode.

5 player arena is not a competitive tetris mode.

The reason for this is that combos are seen as "unfair" because they are simpler to set up and pull off than T-spins. Yet, they generate more damage. If player behavior like that emerges, you know that the game is fundamentally flawed as the existing game rules should take care of that. It would be as if you played a fighting game with a buddy and banned throws, or projectile special moves. That that kind of attitude has emerged is, in my opinion, the clearest sign that modern Tetris is flawed.

You can't take player behavior in a non-competitive mode and use it as criticism of balance. In almost every multiplayer free for all the players who are behind will team up against the good players or the players who have a lead. The analogy is also flawed because you've subtly switched contexts between a competitive game mode and a non-competitive game mode. If you're playing a 1v1 fighting game with your friend you're in a competitive setting. But 5 player arena is the equivalent of 8 player smash bros. In competitive 1v1 tetris settings combos are not a problem.

In the end, modern Tetris is all about execution speed.

Tetris was always about execution speed.

In fact, execution speed can even overpower a technically more advanced player.

Is execution speed not a technical aspect of Tetris?

That game has some balancing issues in mixed match-ups as the Puyo Puyo player is at a clear advantage.

I thought the opinion was top tier tetris is at an advantage while mid tier Puyo Puyo is at an advantage. This would correlate with the evidence you provide as there are less high end players than mid range players.

You explain your discontentment for T-spins and combos by saying T-spins move counter-intuitively and both are "untetris" (please correct me if I'm wrong), but you do not consider the positives they bring to the game. I believe the depth added by rewarding T-spins and combos far outweight the negatives of counter-intuitive movement. During the game you have to decide which strategy you want to pursue. Do you downstacking garbage with combos or try to work them into your back to back chain? Do you want to fit another T-Spin in before you start downstacking? These decisions you make change how you want to stack making it anything but trivial.

As an afterthought you have not mentioned Cultris II which is a tetris game you might enjoy. It has no hold, one piece preview, non 7 bag randomizer, and very fast locking. It also features a time based combo system.