If we consider it relative to HTTP1 just to heighten the contrast, it takes the layers of: TCP connection management and negotiation, plain text framing protoco

If we consider it relative to HTTP1 just to heighten the contrast, it takes the layers of: TCP connection management and negotiation, plain text framing protocols, protocols too limited to deal with the greatly-increased use of or need for multiple streams at once, SSL layering its own negotiation in, rather hacky stories around websockets/SSE (which are usually used as text protocols framed inside of text protocols framed inside of text protocols... not really the best setup), and probably a couple of other things. All of these things were designed for a different era at the very least, and often designed independent of each other. HTTP3 slices through the whole thing and creates nearly an entire protocol stack for its needs, using only the minimum it needs from IP to work over the internet at all. My software engineering instincts tell me this is all a bad idea and those layers should be kept separate as they were, if indeed they weren't already intermingled more than they should be (e.g., SSL & SNI; "why should SSL have to know anything at all about how HTTP deals with host names?" say my instincts). However, I intellectually realize that my software engineering instincts are not calibrated for the size of the HTTP world, nor the amount of resources that can be thrown at this problem. It's a great example of slicing through many layers that make sense independently, but just never quite went together properly, to make something that's going to perform better without 30 years of mismatching layers stacked on top of each other. (I'm not saying HTTP3 is perfect, only that it is a good example of someone at least trying to do what I was talking about.)