For the non-dev user, Gutenberg takes longer and is more fiddly to do what the old editor used to do, breaks a lot of old themes/plugins, and makes it harder and harder to use the old editor/themes/and similar.

For the developer, WordPress used to be really easy to make add-ons for and customize. Now you need to know React to get the most of of WordPress, and if you're going to go through the trouble to get good with React, what are you going to do, use it to maintain WordPress sites or go get paid more to do React development?

Gutenberg and the changes associated with it do make a better site — but people didn't want a better site, they wanted a better WordPress.

They forced it down to people's throats without listening to anyone's reactions or objections.

I have tried to learn how to use it and have lost counting how many times they changed how it works as a whole.

You have no idea how excruciatingly painful is for me to use it that I have 22 years of professional experience with computers; imagine how non-tech savvy users feel when they try to use it!

Not all people are computer literate or are interested in technology in general, what they don't understand?!

Users want a tool to do their job and they want it to be stable, safe, and robust; don't change this concept or you will lose them on the spot, PERIOD!

Instead of letting Gutenberg as a plugin it originally were (well, technically it still is offered as a plugin, but that's another story) - so people can choose whether to use it or not - they forced it to the community and on top of that they are working non-stop on implementing new mechanisms or ideas that cancel previous features, thus leading to a mad chaos.