They don't like it because they don't understand it and it makes them feel inferior.
You know that this is quite insulting? People have many different reasons why they prefer certain music. There is genuinely nothing wrong with that. I don't think that there is any reason to look down on others just because they don't share your preferences.
Also video game and movie music is naturally made to support the emotions transported by text, voice and action that happens on the screen. It doesn't have to speak on its own, quite the opposite. The music in media is not at all supposed to take a front seat and tell something on its own. It's supposed to support. Some "en vogue" projects might include music as another means to transport content but that's quite rare and in itself not something that has to happen or is superior to anything else. So your accusation of people "not understanding" modern music is totally out of place here since there is in most cases nothing to understand in video game and movie music. It's "only" an emotional support and therefore most composers indeed use rather melodic music (or what most people would call that).
I heavily doubt Larian wants to make experients with the music for Divinity. While Kirill made all kinds of different music with different instruments for Divinity, he never left himself the sphere of "mass market music" as you might put it. So why should his successor? I don't think it would be a good fit to this series and its heritage.
Edit: I would also be careful when I use words like "serious" or "professional" in an environment in which I only want to devalue and dismiss certain stuff. Just because you don't like something doesn't mean that it's technically bad or unprofessional...
