I guess it depended on when IS planned to develop Echoes: SoV while the Switch was being planned. Echoes was probably at the point where it was too late to consider bringing it to the Switch, especially considering its using the Awakening engine. Besides, there is a Switch game on the horizon.
As for Warriors, I agree with others that bad timing and a roster that was too focused on certain games kinda took away its momentum. It should've released in September like it did in Japan, or later. Though I don't think Odyssey would've stolen its thunder one way or another since they're both different games and, as someone said, fans will decide what they'll buy.
I'm just glad Fire Emblem is thriving. I love Awakening and I'm slowly, but surely, grinding my way into the older games and I'll get into Fates and Echoes later on. I don't care what the naysayers say. Waifu emblem or not, Awakening is a great game and fanservice isn't really that prevalent as some people tend to overexaggerate at times. And the so-called dating sim doesn't bother me at all as it didn't really feel like one anyway. Fates and Awakening didn't succeed because of fanservice or waifu emblem alone or as the biggest reasons, I believe. They were well-received by critics and have fans that support those games, even if Fates was a bit polarizing.