Earlier quoted context omitted.
300 minutes is 5 hours per week of vigorous exercise. That's... A lot, no matter what
That's ~43 minutes a day, or the approximate length of an episode of a TV show - it really isn't that much.
Yeah, on top of which you have to add 3 times/week 1 hours of weight liftings and 2-3 times week 30 minutes of stretching
Also 43 minutes of HIIT sounds like a nightmare. I do 30 minutes HIIT and I'm completely spent afterwards, there is no way to reach 43 minutes.
Also with 7 days/week of 43 minutes a day + weight lifting your body will be overtrained so injuries will kick in.
Obviously it's a bit different if you do ONLY vigorous training, but then you lose all the benefits of weight lifting and stretching.