I don't think it'll cause too many issues once the generation proper begins and we stop seeing these cross-gen games. The beauty of optimization is that you can always just lower resolution. If the devs can't pull off at least 720p upscaled to 1080p with AMD's FSR on these current gen only games, there is always sub 720p resolutions which can be upscaled to 1080p with FSR. FSR is going to be a game changer for the AMD powered consoles for sure.
You also have to remember Switch 2 is going to be coming soon, likely in a year, and it's specs are certain to be even lower than Series S. If a dev is already going to be porting a game to Switch 2, there is no reason why they wouldn't port to Xbox Series S. Besides, MS requires an S port and they're not going to drop that requirement when more than half of their Series sales so far this gen are S models, and few is the dev that will drop both S and X over the S requirement, when they already have to make their game work on the even weaker Switch 2.