zashikiwarashi Thanks for sharing, I did not foresee this issue. I would think this is a very low priority for developers as of now. If this is indeed a problem as you and the other commentator describe, I think the first step would be to open a ticket on the os issue tracker.
Sharing my experience, I use 3 or more languages to switch between on Gboard. Typically, clicking the globe icon on the bottom right when using the keyboard switches the languages, without any need to open the long menu. Multiple clicks switch languages fast enough. Gboard is also intelligent enough to switch back to my primary once I am done instead of having to click through all languages again. Memorized patterns of 1 click for X language and 2 clicks for Y language and so on, then click again to switch to primary works for me. Maybe this helps :)