This seems to suffer from the "Swiss Army Knife Syndrome": It does many things, but not one thing well.

Any individual "European" (that is, a speaker of a language which uses those Latin-extended characters) is going to want a layout where the symbols they use daily are accessible either as separate keys, or with Shift. Requiring AltGr to type é and è isn't going to fly with users who need them. And I'm certainly not going to press Shift+AltGr+A/O/U to get Ä/Ö/Ü, which I have to type many times per day.

Some parts of the layout also seem to ignore which letters are actually in use. The capital Eszett (ẞ, Shift+AltGr+S in this layout) simply isn't a thing in the real world. It has zero usage in practice. Surely that spot could be utilized for something better?