Yeah, that is an unfortunate trend in the modern web. There's really no justification for this, as those "incompatibilities" are introduced artificially (in most cases, anyway).
Changing the user agent string does a pretty good job most of the time but it's tedious to do for all browsers constantly. I only know how to change the user agent in Firefox, using an extension called Chameleon.
Like @Hackgets alluded to, I also think big corporations are taking over the web for their own profit. In this regard, Google is by far the company with the most control over the consumer choice. This makes it fair game for smaller companies too, albeit with less ambitious goals: supporting one browser is easier than two, therefore it's cheaper and thus more profitable.
Personally, I really dislike how now all personal websites point to a myriad of social media profiles and nothing else. I immediately leave those sites. I'd much rather spend the time reading an article that someone wrote for no other reason than their own interest.