Then the best solution is to provide us with the ability to choose which mode we want. That way players who want only TB can play it that way, and the players who want RTwP can play it that way, and players who want a combination of the two can play it that way, and the players with similar preferences can team up with each other.
Except that turn-based gameplay where you can consider your options carefully, and real-time gameplay where everything is happening at once are vastly different, with different approaches to how things are designed.
In real-time, for instance, enemy attacks have to be less damaging and often highly telegraphed and avoidable. The fights are more attrition-based. Making that turn-based will result in turns which have little impact because the enemy threat is generally lower. In turn-based, attacks are unavoidable except through dodges and misses, and the damage received can be much higher because you have time to consider your options. The fights have more burst damage. Adding a real-time option onto a turn-based game will result in harder-to-avoid, high damage attacks.
You could not just slap real-time combat on the Original Sin games, it would be a completely unplayable clusterfuck, given that a single enemy can deal a lot of damage to a character on one turn alone. You think the complaints about "everything is always on fire" are bad now, just see how it would work in real time.
This is not something you can just slap on as "an option" and call it a day. The demands of the different styles require different approaches in design.
Then how do you explain RTwP games having a TB option? This same argument should equally apply there as well, yet the TB mode in P:Km works very well according to TB fans themselves. Seems like this is a very convenient one-sided argument being made only from the TB side, that all RTwP games should have a TB option but not vice versa because TB games cannot have a RTwP mode something something. I don't buy it for even a second. Seems like a self-serving argument from TB fans so that they can have everything their way.