Tanks are objectively better than mechs; a tank could take down a mech in one clean shot to a sensitive area. Legs on a robot are a horrible idea, they can be disabled or shot and then its fucking useless. Tanks are also more maneuverable than mechs, since they don't need to haul all their fuckhuge equipment around and can simply tread over bumpy terrain, and are a smaller target. So in short, tanks are better then mechs, mech a shit.
Yup. In the real world tanks and planes are more feasible and practical than mechs without a shadow of a doubt. Mechs aren't in the real world though. And that's a large part of the reason I like them. I like that they're a completely fantastical and silly contrivance that has no association with or baggage from the real world and can just be whatever the author wants them to be.
tanks can't parkour like a robot so basically they have no tactical application in the modern battlefields of today
With current technology, this is absolutely true.
But most mecha are based on technology that does not fully conform to modern techniques. You can't measure the scientific merits of a mech becuase there is no real world basis to compare it to. Future materials, energy sources, and other criteria all don't exist in any form yet and are therefor impossible to measure in any meaningful way.
No one understood the basis for what would some-day be an iphone in the early 1900s. The same can be said of quite a bit of future tech.