Apple's end goal is, as you say, to get clangd to work with Xcode. However, having a replaceable transport layer for LSP could benefit lots of people other than Apple.
Ie so far the "lots of people" have not materialized, even outside clangd.
I can certainly think of use cases for such a thing, but most people seem happy enough with json-rpc at the moment.
Part of that is likely that trying to speak LSP over a non local connection may be a fools errand anyway. It's a chatty protocol no matter what the transport.
JSON-RPC has several alternatives that very large software companies have vested interests in: gRPC and XPC.
You seem more knowledgeable of these technologies than I am, though. It just seems to me a good thing that 1) Apple, and consequently, all iOS and macOS developers will be using clangd, and 2) Apple is putting significant effort into improving clangd. I'm not sure why any of that news or optimism needs to be quenched.
As for 2, all I'll say is based on history in llvm projects, I'm not anywhere near as optimistic as you. The history here is simply not one of all great things. The PR is, but the reality is much more mixed (some really great things, some really not so great). So while I certainly am hopeful, it's definitely not the unbridled optimism everyone displays here.
In this case, the collaboration with Apple and Ericsson on the underlying architecture has been going on for a while, and while not everybody always agrees on priorities and design details, I'm thrilled to see Apple double down on their involvement here!
Heck, last time i asked him (a few months ago), even Chris Lattner agreed with my view, and he used to run his stuff at Apple, so i don't think it's unreasonable.
I think it's perfectly okay to be cautiously optimistic instead of fawningly happy.
Do you actually have data or a real argument you'd like to use to suggest otherwise (IE that it's been all overwhelmingly positive?)
We also just talked with Apple folks at Euro LLVM about this, and while the plan for the near future is for them to have a transport conversion to JSON-RPC, I expect them to want the more fine grained control in the long term.