I understand your dislike of the default workflow for Firefox profiles. Fortunately you can launch them from the CLI, so I usually creat an alias to my alt profiles then launch the browser from the shell.
I still use them because combined with https://addons.mozilla.org/en-US/firefox/addon/open-url-in-c... ( https://github.com/honsiorovskyi/open-url-in-container ) is a game changer for my workflow but it does make me sad that issue has been open for so long
Multi-Account Container nicely reduces the need to juggle different Firefox Profiles, but it doesn't eliminate it. (I certainly still use a mixture of both for a myriad of reasons.)