No it’s not. Contagion spread is logarithmic, and has obvious upper bounds. E.g. about a third of the us has gotten Covid. 5x contagious does not give you 166% of the population infected. Nor does it give you 100%. Probably not even 90%. I would bet no more than 50% over the next year.

Half as deadly on the other hand is a big deal. It’s not just deaths, it’s also hospitalizations. If you imagine the bell curve of outcomes, the deaths are the small tail on the right and the hospitalizations are the fatter bit on the right. If you get to move everything to the left a bit, you remove the biggest chunk of the population from getting hospitalized in the first place.