I worked in an organization where UI was free to adjust and it did not work for teamwork. Too many variations. Something that worked for one did not work for the rest, it was painfully slow to assist each other on each other's computers. Involved partial constant re-learning of a new environment. It was a hopeless bunch of individualists, not teamwork.

Saying that with admitting Apple's decisions on 'improvements' are many times controversial the least. They, as many vendors of products nowadays, forget the old saying "If it ain't broke, don't fix it". What is worse, they tend to 'improve' or 'revolutionalize' (and nowadays 'disrupt', yeah, they distrupt all right!) things working perfectly and desirably!

I also admit that careful customizations is desirable.

Just like standardization, standardization is desirable too! Standardization has lots of merits.