The performance benefits are aimed squarely at the large, entrenched interests who can absorb the increased costs as a rounding error. HTTP/2 and SPDY/QUIC look, to me, to be about decreasing costs and increasing efficiency for large web hosts and erecting barriers-to-entry for competitors.
HTTP/2 is more complex to implement from scratch (but still quite doable, even as an individual), but it has built-in support in every language & framework worth its salt now, so you don't need to do that.
If you're using an existing implementation, that's usually just as easy to do as HTTP/1.1, because they have almost exactly the same semantics (that's an explicit goal from the spec), and so most implementations have almost exactly the same API.
In practice, it's a syntax & connection management change on the wire that's mostly invisible as a developer building on top of it, plus a set of optional extra features (like Server Push) that you can use if you want or ignore if you don't.
Can't speak for QUIC/HTTP3, since I haven't touched them yet, but I'd be a surprised if that's a hugely different story.
I mean, who are these newcomers we're talking about? There's basically never a reason to roll your own web server. I guess if you want to compete with Nginx, sure, the barrier of entry is a higher now? But that's an incredibly niche case.
