Blade is the best entryway for an R-rated MCU movie, however there was by no means any actual expectation of that occuring. Marvel wants to begin seeing diminishing returns earlier than they will take into account making a function movie that is not accessible to a youthful viewers. I do not suppose they even intend for any grownup Disney+ reveals within the close to future.
Additionally, if it was rated-R, the utter disappointment of seeing Blade’s violence neutered to PG-13 in Avengers motion pictures (or even when/when he’d present up in one other character’s film) can be immeasurable. Marvel does not want that backlash when it is a lot simpler to keep away from from the beginning.