This does keep coming up, and it's a few years old now. I think Quicklisp can easily still support https while supporting the older packages that are tar+http, which could easily be mirrored in a git repo. Quicklisp has unfortunately taken over the entire ecosystem, making it hard to use anything else, and you often need to depend on it to use a lot of tools in the ecosystem. It sort of reminds me of Systemd in that way.
I agree on the version pinning being a worse situation, and also not having something like "node_modules" for lisp. I haven't tried CLPM since a while back, it was kind of hard to setup back then.
I have a little package manager thing, cl-micropm, that just uses Quicklisp to fetch everything via docker (should probably support podman too), and an .envrc file to tell ASDF to look in the project directory (a project-local node_modules-like folder called "lisp-systems") for systems. That way I can pin my deps manually by picking the commits + git submodule in lisp-systems/, and it's isolated to my local project. I looked into using the Docker container to rewrite the requests to use https, bypassing whatever Quicklisp is doing, but I never got around to that.
I'm looking to switch it to something even simpler/explicit though, cl-pm, that'll only optionally need/use Quicklisp via podman _only_ to figure out what the dependencies are, and then just have a function that uses wget/curl/git-pull to conveniently explicitly pull them in on request. That way you can decide to add a git mirror for an old http library, or pin a specific version, etc. It's slightly more manual than Quicklisp or CLPM, not a big deal, but very easy for anyone with just a little bit of lisp knowledge to understand the whole thing in under an hour.