This isnt true. TB system is a niche and favored by some, but real time gaming is basicly the standard in all games, ecxept those which are pure tactical (civilization etc). Im pretty sure this will reach a broader customer base if it is real time, or we had the option to choose. The reason D&D is TB is because it is not a video game. There are plenty if things in BG3 that doesnt reflect D&D, so this should not be the reason to exclude real time combat.
If they want the game to reach heights like Dragon age, Witcher and Skyrim they need more immersive combat in real time to appeal to the average rpg-joe.