it is worth it to make combat minisculy slower to ensure the game is played properly. The majority of time in combat isn't even spent deciding reactions, anyway, even when you play actual 5e D&D at a table. In fact, usually reactions happen rapidly as players quickly state they want to interrupt the DM's action to use it. What takes forever is players deciding what to do on their own turns for their action and bonus action, and that crap isn't going to change regardless.
I have to point out that Solasta, another game based in 5e, implemented in the kickstarter demo the usual reactions in the enemy´s turn.
Maybe not perfectly in the demo, and the game is still in development, but it shows that you do not need to use on-off automatic reactions to play a D&D 5e videogame.
Usually most strategy games have a "speed bar" "faster turns" "automatic turns", etc so for people that find an eternity having to wait a second more and that way we could have a proper reactions that require player input. I think the tradeoff works well for me. I prefer having more features instead of less delay.
TB combat is not going to be fast-paced anyway. Might as well they allow us to play it properly.
As stated in another thread, instead of predetermined reactions without a player input a pop-up dialogue in the enemy´s turn could be a feasible alternative. Several people discussed some ideas on how to do that there.