However, I don't think designing an interface that is good for both is fundamentally difficult. The problem comes from evolution. In early versions, with only a few features, none of this requires a ton of thought. As features are added, it's rare that an overall UX re-design is undertaken, for a few reasons.
For one, the people working on it and using it day to day are incrementally learning changes, and have time to adjust. In some cases they probably don't even notice the UX learning curve problem as it takes time to become apparent.
For two, existing and power users will freak out if a new release changes shortcut keys or otherwise "moves the cheese". Think of the outrage if vim were to announce "we're changing all the commands to be fully consistent with each other, but it means every command you've spent years memorizing is now incorrect.
Even for the most UX-focused team it's impossible to predict the feature set a product will have in 1, 2, or 5 years, so of course by the time you get there, the UX has issues.
This was the design goal for Blender 2.8. Both of your comments seem to be based on using earlier versions of Blender.
Both Vim and Blender are very hard to learn and discovery is extremely poor. There is just no way to figure it out without reading the manual. Even after you read the manual, you have to practice it frequently to get good at it. After that it's a dream.
I don't really like characterising a UI as "good" or "bad" in a one dimensional perspective, because whether I will choose an easy to use or an easy to learn application depends entirely on what I'm going to be doing. For example, with video editing (and also code editing), I'm doing the same actions over and over and over and over again. I'm also combining actions in different ways and I want a kind of "UI grammar" that lets me efficiently express myself without searching around for some drop down or macro. I use these tools for hours on end, day after day. I don't really care about ease of learning -- I only care about easy of use and efficiency.
For other things, I really care about ease of use. For example, I make New Years cards once a year. I want some software that helps me make a mailing list, print an image without screwing about, etc, etc. I don't want to spend more than about 30 seconds setting it. It needs to be intuitive. If anyone knows of such a thing for Gnu/Linux, I'd be very happy ;-).
Frequently ease of use and efficiency are at odds with ease of learning. Best if you can do both, but often you have to compromise. Both Vim and Blender compromise a lot, but they are aiming at a particular niche. Not everybody likes them, but those that do love them. Some other applications compromise in other ways, and at least for my applications I don't find them appropriate. YMMV.