Or look at it this way. A unmounted unit isn't completely screwed for having 2-3 less move and the player is forced to make a team that caters to specific maps rather than a team of 242434 paladins that have WTD control, high move, and balanced stats. Characters all seem to have thier own uses and are more unique in 5. It actually makes you want to try out more characters so you have an indoor and an outside team. I mean in any other FE, a character like Ronan will never be used outside of being forced, but sometimes his 7 base move and 3 movement stars will make him a good character to bring just to make rescue chains early on.
Except mounted units still excel indoors it was only Falcon Knights, Wyvern knights, Great Knights, and Duke knights that were greatly nerfed by it. Paladins, Mage Knights, and Forest knights were mostly untouched by dismounting. That and all your lances go to waste as no one onfoot can use them.