Some downgrades are of course inevitable, but the Switch version of Forces took it too far. It looked worse than Sonic Lost World on Wii U but ran at half the framerate. Switch may be weaker than PS4/Xbone, but it's not that weak.
Switch is the lead platform in sales, so it should be the lead platform in development, it's only logical.
Well, there is no way to compare objectively, since Lost World wasn't released as a multiplatform barring the Steam release which in itself is a port. I kinda feel there is more going on in Forces, though. It certainly plays a lot faster.
To use a multiplat example, Generations looks better than Forces on Switch and we know for a fact that Switch is considerably more powerful than PS3/360. PS4 was clearly the lead platform and the Switch version was clearly cut down from that one fairly haphazardly.
In light of the sales however, it makes more sense to make Switch the lead platform for future entries; make them the best they can be on that platform, then just bump the res and other settings up for PS4/Xbone.