Larian stated in a interview I think it was that they want to shoot for a more realistic version of combat, were combat flows well, a reaction system would interrupt the flow and it would be highly annoying in multiplayer (I've said this before some where).
They said it, and it was every bit as bogus and false then as it is now - A proper reaction system would never slow down the game by any noticeable margin alongside the magnitude of the innate slowdown caused by multiplayer characters actually deciding what to do with their turns. One is always going to be insignificant alongside the other. You can draw a fairly legitimate tabletop comparison here - Sometimes a player will, indeed, hesitate for a couple of seconds deciding whether to burn their reaction on something or not - but that few seconds, IF it occurs, is insignificantly small compared to the simple time that other players take to decide on their turns. Claiming that reactions would interrupt game flow and cause slowdown in combat is utterly false, and a poor excuse - another contemporary game illustrated and proves this beyond any shadow of a doubt, and Saito Hikari posted a very instructive demonstrative video about this a little while back. A few, in fact: (
Here), (
Here), and (
Here), and I'd really strongly encourage others to take a look at them before they think about claiming that proper reactions slow down combat - they actually don't. They make it more reactive, more engaging, and overall faster paced as an end result.
I have a personal suspicion about why the Larian statement is that a proper reaction system would interrupt the flow of combat and be annoying in multiplayer, but it's not a charitable opinion.
