This is all very interesting and is why I created the poll on current CP usage/uptake. I confess to sitting on the fence at the moment. For lots of reasons (not just Gutenberg), I am very reluctant to stay with WP but, at the same time, I can’t bring myself to commit to CP. And, with around 30 sites to manage, I know, that I’ve got to make a decision one way or another very soon otherwise I’ll be left with a big mess.
As @ElisabettaCarrara said, the CP devs are all volunteers with other jobs. I honestly don’t know how they find the time but I have the utmost of respect for them . Without them, we wouldn’t even be having this discussion. Even so, this for me remains one of the reasons why I am reluctant to commit. And as @azimpact says, I’d also like to see a much higher adoption rate – another key factor.
Getting plugin developers on boards is essential too – but which ones? As @Marialena.S says, WP / CP needs a decent media gallery. To date, where necessary, I’ve had to resort to using a paid plugin – one of the most widely used ones with both free and premium versions. But this plugin is so symptomatic of everything that is wrong with WP – huge bloat and badly written code everywhere.
As an example, I had an album page with 22 galleries and a total of 5500 images in all 22 galleries. The album page, even though it consisted of nothing more than 22 small, optimised thumbnails, came to a massive 23MB (uncompressed). Google PageSpeed and, more worryingly, Google Search Console, both crashed when trying to crawl that page. Having studied the source code, I noticed that each gallery element had data attributes containing around 4KB of JSON data for every single image in that gallery. Very sloppy and lazy coding and definitely not something I’d want to see in CP.
Anyway, I don’t mean to be negative. You have no idea how much I want CP to succeed, and I would be the happiest little bunny 
on earth if I could finally dump WP. But I guess I just need a little more convincing that CP is going to work out.