Well, Nintendo EAD are vastly better programmers than Sonic Team.

This is a bad trend and looks like Doom set the FPS standard.  Doom is understandable as the graphics powerhouse that it is, but this game should not be at those same expectations.  I would expect at least 1080p docked or higher framerate.  Sadly, I think Mario Odyssey set the 720p standard. I know we are still seeing the limitations of the system, but we have also seen some pretty impressive outcomes with some titles.  I think it comes down to an efficiency issue with how the games were designed and developed and the amount of time that the developers are willing to put into the port.  I would say that it is much easier to just make a PS4/Xbox one port 720p and 30fps and call it a day.  Take NBA 2K18, sure the game has pretty high visuals, but the files sizes are outrageous.  I do not think that developers are at an acceptance with Switch where they are willing to dedicate their development cycle to these considerations just yet.  As they game more experience with the system and Switch keeps dominating the market in the upcoming year, we will likely see these trends change but how long until is the issue. 

I really wouldn't say Doom is "way more technically demanding." Both games are very different in terms of design and art style, but both are gorgeous looking, current gen games. Both games are also made for current gen hardware, and both games feature the same resolution and frame rate in both docked and undocked modes. The same is also true of Rocket League, which managed 60 fps in portable mode and has 720p resolution in both modes.  I think people are overestimating how much of a boost Switch games get in docked mode. No boost in resolution and frame rate in docked mode ain't just a Sonic Forces thing. I've no doubt Wolfenstein 2 will have similar issues. There is more to a game's graphics than resolution and frame rate, and its very possible these demanding games simply need to put the extra power docked mode provides into other things that will help them look better on a big tv.

Docked or undocked, the Switch is still a console with a mobile processor trying to run games that were designed to run on hardware FAR more powerful than it.

You're comparing a first party team with a 3rd party team, not really a fair comparison. Sonic Team has to optimize Forces for XB1, PS4, and dozens of possible PC hardware configurations in addition to Switch, Nintendo EAD only has to optimize for Switch. Rare is the 3rd party game that can match the graphics of the exclusives on any platform. 

To be fair, Lost World was made by Sonic Team's "B team", while the more skilled "A team" was working on Forces (Forces has been in development since shortly after Generations released). It is true that Sonic Team are no longer known for being particularly skilled at programming like they once were in the 90's (the Yakuza team now has Sega's best programmers), but I wouldn't call them bad at programming either.  

This is a bad trend and looks like Doom set the FPS standard.  Doom is understandable as the graphics powerhouse that it is, but this game should not be at those same expectations.  I would expect at least 1080p docked or higher framerate.  Sadly, I think Mario Odyssey set the 720p standard. I know we are still seeing the limitations of the system, but we have also seen some pretty impressive outcomes with some titles.  I think it comes down to an efficiency issue with how the games were designed and developed and the amount of time that the developers are willing to put into the port.  I would say that it is much easier to just make a PS4/Xbox one port 720p and 30fps and call it a day.  Take NBA 2K18, sure the game has pretty high visuals, but the files sizes are outrageous.  I do not think that developers are at an acceptance with Switch where they are willing to dedicate their development cycle to these considerations just yet.  As they game more experience with the system and Switch keeps dominating the market in the upcoming year, we will likely see these trends change but how long until is the issue. 

Could be CPU issue and its safe to assume they're were building with PS4/X1 specs as the priority.

Sonic Generations was 30 fps, wasn't ideal but still very playable.

I know that there is a reason, there is always a reason, good or bad, I'm just saying that people should not buy a 30fps sonic. It's really not as good, and being able to play on a portable does not make up for it.

That depends on the individual. I think a lot of people would consider 30fps a fair trade for being able to play it on the bus/train or on their lunch break, especially considering previous 30fps Sonic games like Generations and Colours have been well received.