The older umpires experience skill decline like anyone. Most of them just shouldn't be umpiring. Some of them just weren't ever good mlb umps to begin with. Hernandez by every standard has been objectively bad his entire career AND he's a flaming pile of poo as a person. He's not even that popular among the union guys, but the train of thought (again, union mentality) is you do that with him, flood gates, locusts, famine and the world ends.
There's a better way and Hernandez literally can't see past his nose anymore (he couldn't ever, really) and shouldn't be an MLB ump. There should never be a situation where you're correcting 5+ calls in one game due to one guy messing everything up constantly. Bad calls happen, that's why there's replay - and even that's not going to solve all the problems. But last night was past inexcusable by any standard, let alone a playoff series between your league's two marquee franchises.