I feel like I should chime in here and say that environmental effects absolutely should be a thing in 5e, and Larian has helped me to see that.
Ever since playing DivOS I started incorporating environmental effects into my 5e and other TTRPG games and they have greatly improved because of it.
environmental effects ARE a think in 5e. But you get a save against them, and not all spells create them, but lots of things clearly state they set things on fire. Right now, as implemented, too many things make them, and the lack of save against the effects makes them a bit out of place
