There is a time to mash and a time to spin.

If you mash all the time, you are probably losing performance somewhere.

If you spin all the time, you are probably losing performance somewhere.

Though anecdotally, when young, I mashed. I could pull off from a dead stop in a very high gear ratio and accelerated quick and keep going. As a much older person, I can't begin to even think about doing that. But I can spin and climb the short hills here as well as most. At least better than the young noobs that try to climb in their small cogs at a 30 cadence.