Are you familiar with the concept of "Casting Time" at all?
Yes, but I'm not sure how that tracks. Are you saying TB you start casting and other people take their moves? then your spell goes off. To be fair, I haven't played a game that supports that but yes, it does nullify that one point
Also I like how you conveniently ignore real time with pause innovations when it's convenient - like the most recent RTwP systems having re-target abilities for spells (pillars of eternity 2 and kingmaker) which completely nullifies that line of thought.
yes, I am unaware of those innovations
Furthermore, how would you even translate Reactions to a RTwP system? Reactions are EXTREMELY important in D&D 5E.
well, I am not a 5e D&D expert but so far reactions have things like counter spell or things like that. It's easy enough to flash a button when a reaction is available it's also fairly easy to select a "mode" (i.e. if I can, always counterspell my current target) with all kinds of options. Same way modern games implement contingency type spells.
Again, all of that aside the bottom line is that TB does not support MP as well as RTWP. In addition unless you're advocating it to be TB all the time (as opposed to just in combat) you have the transition problem (do we leave the 50 npcs to take their turn or do we transport to a battlefield without them). RTWP allows you to have engagements anywhere, anytime and you don't have to do a transition.