5 gallons isnt too bad for tank size, photos dont do much justice anyway.
10 gallons isnt a wast of space for 3 bettas if they are all happy and healthy.but it seems they are healthy and happ in your tank.
is your tank heated and filtered, if it isnt filtered, more water changes are needed IMO
again, personally i think having too much stuff on the bottom is a waste for bettas, yeah a few decorations such as the budda and maybe a cave looks good, but bettas are mainly top dwellers and only venture down sometimes.
i think what people meant by busy is theres a lot going on, but to me its a good thing, like you say, boring plain tanks with a plant is crap, yeah do have a lot of good things in your tank, but some not nessary.its your tank anyway, and aslong as your bettas are killing each other, and your happy with it, so be it.
i do also get the little feel that you are a offended by what members said, please dont be (and sorry if i misunderstood) people are just trying to give comstructive critism, and help you out a little, maybe saying what they think and not whats best, such as i would get rid of this ect, not there fault, i do it too, we all do it, its just what we say...you ask for our opinion, so we give it
no offence, be training your betta to jump isnt hard, most bettas will do it, all mine do, not trying to put you down, just saying
the betta in a bottle looks cute