Yes, big maps tend to generally increase the skill gap between players. However, the contrary is the case on smaller maps, where skill differences are sometimes less impactful.
I share your observation that particularly in matchmaker, teams with very large skill differences can lead to a frustrating experience for the opposing team. Note that the matching algorithm tries to avoid these pairings, but they are unavoidable when people team up for the queue. Back when TMM was new I was quite often running into one particular team of one 2200 with a couple 300-600 rated friends. To avoid the frustration, I ended up just adding them to my friendlist and only qued myself when they were already in a game.
This is an issue that somewhat fixes itself over time as ratings adjust. And it's also jucy to read the complaints post of certain 2k+ rated players on the forums when they realize that they are suddenly incredibly overrated.