We have user accounts, Read/Write/Exec for User/Groups. Read can grant access tokens which solves temporary+remote requirements. Every other capabilities model can be defined in those terms.
I'd much rather see a simplification of the tools already available, then re-inventing another abstract machine / protocol.
I hope we'll eventually get a fundamental shift in the approach to software as a whole. Currently, everybody is still experimenting with building more new stuff, but it is also a great opportunity to re-evaluate and, at acceptable cost, try to strip out all the cruft and reduce something to its simplest form.
For example - I found an MCP server I liked. Told Claude to remove all the mcp stuff and put it into a CLI. Now I can just call that tool (without paying the context cost). Took me 10 minutes. I doubt, Claude is smart enough to build it back in without heavy guidance.