First, I'd like to emphasise that my time so far with BG3 has been excellent and I intend to post some positive feedback once I've played it some more. In the interests of providing some constructive feedback, I think I've finally realised why I'm not keen on environmental combat.
I didn't especially like environmental combat in the Original Sin games (surfaces, surfaces everywhere!), but it was an original combat system designed with a focus on elemental interplay, so... fine. I couldn't put my finger on exactly what bothered me about it until now, and it's because D&D highlights it:
Too much environmental combat takes the spotlight off the characters.
One of the core principles of D&D is that your players should feel like heroes. Even if they're morally dubious, they should feel like the ones in the limelight, making the difference, turning the tide, and that's never truer than in combat. When many (most?) combat encounters are designed with the expectation of the players utilising the environment, it takes the focus away from them showcasing their exciting new spells, weapons and abilities, and it places it on an oil barrel. That might have been okay in Original Sin, but in D&D it's a cardinal sin.
The environment can absolutely be a part of combat, it just shouldn't frequently be a more effective way of defeating enemies than your characters' actual combat prowess.