Blesta works better when they are all on the same page and training someone to work at their speed and quality doesn't come lightly, you can hire hundreds of developers but if they aren't connecting or working to your high standards and quality then you have to go back and re-do it. And then you become a competitor to Blesta who patches up silly mistakes and fixes for features which have been broken due to lack of QA testing.
There's 3 developers at Blesta. You can speed up developer hire developers who don't stick to the rules and quality and talk to you etc and then yourself and me would be complaining that the code has gone to shit and buggy as hell. Do you want that? No then there you go. You forget a competitor has loads of staff and their software is buggy as hell and insecure with their own PHP Global function PHP took out because they are that lazy.
I know loads of people who use Blesta for selling domains and hosting and it works fine, what they do want though and many others like yourself is a way to set a renewal price and transfer price and more features but they DON'T stop you selling domains. So yes it works for hosting companies, hell I used it for my web hosting business back in the day.
You can't win everything. You do the domain manager people complain about the other stuff like lack of modules / gateways unlike their competitors. You do the modules / gateways then people complain about the domain manager. You can't win so they are doing both.