In reply to Nick.

Just to note, the Classic Editor was more than just TinyMCE. It was a whole interface with panels for meta data (non visual data). It had action buttons above TinyMCE that helped insert things like media easily at any time. TinyMCE was only one small part of the Classic Editor UI, and the 5+ million people using Classic Editor over the Classic Block likely need it for more than TinyMCE alone.