Minecraft always took a little to load. It used to be like 45-50 seconds. Lately, it has been taking an average of 20-30 minutes. I have bedrock on the switch. It has been happening since the nether update was released. I have seen other answers for this, like restarting, deleting worlds and add-ons, but none of these worked. I know that some people delete all their save data, and it works for them, but I put over 1000 hours of work on it, so I am not willing to do that. Is there any other way to fix this? (Also I have the game card.)
I, too have the Nintendo Switch version of Minecraft as well as some other consoles, and have also noticed that it takes a considerably long time to load. Some fixes are:
Deleting unnecessary worlds ( Things like worlds that you once started but never went back on )
Making sure you have a stable internet
Archiving other games that you have on your Nintendo Switch, and saving as much space as you can
I have actually used some of these in the past, and now whenever I open up the game, it only takes about 10-30 seconds to load up!
NOTE: Archiving your games will not delete any of your save-data.
I suspect your wifi is the issue. Xbox integration is really garbage and if you have extremely bad internet (i.e. using a phone hotspot) the app will often crash and not be able to load in. If your wifi is bad this is likely the issue, although I don't know why it would have suddenly gotten much worse and if this is the case I doubt the update was actually the factor.