Reactions are one of the main appeal of combats. Being able to do something during your ennemy's turn is something that doesn't exist in video games except for AOO and "ready" action.
It allow so many possibilities and combats feel so much less frozen / more alive. It's a huge improvement of the TB system (even if the "how" may not be perfect in Solasta).
On top of that If Larian had properly implement reaction (and DnD bonus action) they probably wouldn't have implemented their shitty new bonus action that breaks a big part of the game.
"We don't have enough things to do per turn in D&D" is another myth brought to justify poor choices/poor understanding of D&D's potential for video games. A reaction is something to do.
