My feeling as a top atomic player over many years is that playing variants has had no negative impact on my regular chess skill. If anything it's been positive as atomic has taught me lessons about preparation and psychology that are applicable to chess. Of course, spending time on variants can take away time that you would otherwise have spent on regular chess and have an impact that way - but no different than if you started spending more time on computer games/football/relationships/anything else.
If you want to get worse at chess then it's easy; don't study any chess. It's wrong to then blame the things you did instead for making you worse.
Amazing insights Illion. I do like to play all the variants on vchess and pychess, and it helps me make strategies with a different dynamic or a ruleset, which is good for my mentality, but might not contribute to my normal chess knowledge directly.
I have been playing shogi regularly since the lishogi site was created 6 months back. Shogi and Crazyhouse opening theory is vast, and unexplored, so even attempting to study a bit of theory for these games, does improve my normal chess stamina.
People have the notion that if you play crazyhouse and atomic, you will be only stronger in tactics, as there is no endgames with few pieces in crazyhouse and no non-trappy line in atomic, the notion is not exactly correct. Crazyhouse can also get positional sometimes when you play some d4 systems, and atomic is quite positional at the high level, as top players are aware of trappy lines and just side step it.
tbh, I was a much weaker and one dimensional self-taught chess student before, I started exploring all the variants and getting serious with ZH and shogi.
I have a doubt of my own. I do play the game of Go too, which is played with static stones on a 19x19 board. The game objective is quite different from chess/shogi, as we have to capture territory. I wonder if playing more Go, makes you a weaker chess player, or it makes you more positional or territorial chess player due to some transfer learning?
I believe the main argument for the claim that "playing variants will make you weaker in standard" is mainly about the concern, that you will form new instincts, reflexes and pattern recognition habit and these newly and RECENTLY formed habits might interfere with your usual pattern recognition when you switch back to standard chess.
If this argument is valid or not, depends on the context that follows up:
If you play variants, which require way more different pattern recognition than chess, lets say racing kings etc, and play these variants exclusively, obviously and logically you will have a lack of practice in chess, relative to the scenario where you have spent your time with standard chess instead of RK. Imagine you are a basketball player, you don't even touch the ball or train but simply just train fitness. Could you expect that you'd improve yourself as basketball player? If fitness analogy does not seem so fitting, simply imagine playing full-time Handball and expecting that you'll be in perfect shape when you get on the court to play professional basketball. Main reason as you won't get better as basketball player by only playing Handball is that you simply don't train basketball in the very first place.
To get better at a field, you need to train in that field directly. This is a must or a pre-requirement for the main development.
With other words, one cannot expect to improve at the main field by solely training in a variant thing and expect that the training in that side-field will transfer to the main field enough for you to REPLACE your training in main one.
As we can see, problem arises when we wish to transfer the benefits of a variant to our main field as a replacement of the training in the main field.
So in short, yes, playing solely RK, Atomic etc. won't improve you in standard chess in long-term because the transferred benefits from these variants cannot be replace the training in the standard chess.
However, on the other hand, as for enhancement training, like a basketball player trains different parts of body in fitness to get stronger and improve stamina in a game etc., playing these variants can have definitely benefits if use implement them in your training properly.
After all, first and most obvious gain will be in your ability to think OUT OF BOX.
Closer the variant to the standard chess like 960 (only variant with no any additional game rules except the starting position and adapted castling rules), the patterns specific to that variant will be similar and the amount of direct transfer will be higher for this purpose. By playing 960, you will learn how to harmonise and coordinate your pieces, you will learn how to play in unusual and original positions, you'll learn to handle dynamic, complex positions, improve at tactics from different angles and so much more that i cannot list them all here.
Far away the variant to the standard chess (RK etc), benefits will be more indirectly, in a sense that you'll improve at original and creative or out-of-box thinking. There will always similar strategies specific to that variant that you can directly carry over to standard chess in some way, but the amount of these strategies will ofc be limited.
Crazyhouse could be a good example for the mixture of these direct and indirect benefits, as it is not as far as RK etc. to chess, but not as close as 960 to chess. Stands in-between, on the closer side to the chess imo.
Concretely, by ZH you can improve a lot in your tactics and calculation skills, your imagination for attacking and safety, your feel for the initiative and your sense of time (in tempo as measuring unit). Moreover, it is also very very positional game, because to execute all these concrete attacking tactics, you first need to prepare it right? How do you do that? By identifying weaknesses. You need to know WHERE to attack (strategical part) to figure out HOW to attack (concrete tactical execution). Crazyhouse magnifies simply the weaknesses in a position and the force of attack that punishes these weaknesses. With otherwords, it lets you experience this interplay between strategy and tactics in greater and more vivid magnitude. When you switch back to standard, you will be much more sensitive to weaknesses both from the attacker side and defensive side.
Bottom line is: BALANCE. If you mainly want to improve at chess, variants will definitely might help you as ENHANCEMENT of your creative thought-process, but they cannot replace the main training. As long as you balance the training between main training and enhancement training in terms of amount, you can only get better as a player and more all-rounded!