You know, whenever Sakurai talks about why a certain character didn't make it in, I do think his reasoning make enough sense. You may not agree with him on Ridley, but he simply doesn't think making what is normally a huge imposing dragon into a dinky little thing doesn't do the character justice, and a lot of people would agree on that. And with Chrom, Robin just stood out to him as way more unique and interesting. People say "but...Lucina!" but she was obviously added in at a later date when they weren't so concerned about adding unique newcomers and just needed some extra clones.
Now, if you want a true bull****ter, check out Ryota Niitsuma, the big cheese behind Marvel vs. Capcom 3. Literally none of that guy's reasoning for excluding characters made any sense, and he kept contradicting himself way more than Sakurai ever has. He said that "Strider didn't fit in with the concept" and "we couldn't fit in Ghost Rider's bike" and "Nemesis would raise the game's ratings" and "Mega Man didn't have enough moves" (lol). Of course, Strider, Nemesis, and Ghost Rider all ended up as playable anyway later on.