As a former competitive FAF player I preferred less complex maps because you can more easily manage everything that is going on and focus on a smaller number of more impactful decisions. Complex maps are a scramble to get all the mexes, reclaim, drop expansions, eco/upgrade quickly and perpetually, and then manage lots of things simultaneously as efficient as you can for an extended period of time until someone messes up. There is definitely strategy there, but for me it feels diluted because the speed, endurance, and multitasking overwhelms whatever thoughtful decision making and creativity I might have been able to perform in a simpler setting. Given the focus on large numbers and scales in the games engine and marketing I am most likely just asking for the wrong style of gameplay.
I do not think the size of a map is the most important factor in how a map plays. There are frantic 5x5 maps where you have tons of reclaim/mexes and rush to build as much as fast as possible, and there are 20x20 maps with more manageable and slower gameplay. It seems silly that both ladder and tournaments categorize maps by their size rather than how they actually play. 5x5 maps do provide certain gameplay styles that other sizes of maps cannot, such as base trades and weird close quarters low eco standoff type games. These unique styles are the reason why I think it is important to keep some certain 5x5 maps in ladder and tournaments. I have always been unhappy that less 5x5 maps get included in ladder and tournaments. Even when they are included they are just reluctantly thrown in based on their size rather than to get the unique gameplay they offer.
If the point of 1v1 ladder is to test players skills and rank them accordingly, then player preferences are not relevant to the composition of the map pool. It's about competition, not maximizing player count. The pool should consist of maps that test the skills FAF has deemed competitively important. All of these skills should be tested to roughly the same degree in each pool so that rating, and the experience in general, is consistent. If players do not enjoy what FAF has deemed competitively important then FAF can change what it focuses on, or players can stop playing competitive modes.
The problems are that there is effectively nobody deciding what skills are important for competitive FAF. There is just some list of maps that, on average, people agree are not trash. Maps are categorized primarily by their size, rather than the skills they test. Tournaments are all hosted by whoever feels like it and they just make up the map pool on the spot with no official rules or guidelines. There is no game designer with any control over what competitive FAF is supposed to be.
It seems that since GPG stopped being in charge there has been less focus on 5x5 maps in competitive FAF as time goes on. Competitive FAF even includes maps with modded behavior like crazyrush (mex duplication) and loki (scripted reclaim values). People seem to have concluded that maps with crazyrush levels of deviation from the norm should not be included in matchmaking anymore, but they somehow justify including them in official tournaments anyway.
Some team, or individual, should decide what skills competitive FAF wants to be about. Categorize the maps based on the degree to which they test each skill. Official tournament and ladder map pools should then be constructed to test each of these skills to a consistent degree in each pool.
Alternatively, if the point of 1v1 ladder is to maximize the number of players, and the average level of fun had by those player, then everything above should be disregarded and maps should be determined by polls and forum arguments.