I had a couple of problems with the profile manager.

For one, there's now two profile managers that do not work together. You can't use an old profile in the new profile manager or vice versa. You can access the old one via .desktop entry or from the CLI. But you can't access the new one from the CLI.

It's also a bit buggy. For example, if I have my "Personal" profile open and middle click the Firefox icon, it will open up another "Personal" window rather than show the profile manager. And to access the new profile manager, I first have to aim for a tiny target (especially tiny on my 100% scaled 4K monitor) and do 3 clicks. With my solution, I explicitly choose which profile to use from my dock.

It's also hit or miss on which window a link from an app will open up in. Whereas with my solution, I can set "Firefox (Personal)" as my default browser and always have stuff open there.