Indeed. Well.. How could one not like MAME?
When folks say they don't like MAME, it stinks, it SuX0Rz, it can't even play game xyz right blah blah blah, they are usually referring to one specific aspect of the program. Not MAME overall.
Personally I dislike the bloat and the tedious setup.
Dislike that not all options like are saveable from the GUI.
The whole UI seems "off" a little unconventional and incomplete at times.
Dislike that that there is no clear and concise description of the hierarchy of config files.
The beyond ridiculous software lists.
The annoying forced minimizing of the main GUI when focusing on something like Notepad.
..and so much more..
But of course it's essential software which has been around for decades now. It's easy to see it as a plug-in "module" for modern OSes that adds capability.