It is a shame when poor umpiring ruins a game. It is a hard job though and to be fair without umpires we wouldn't get a game. That said, a Level 1 umpires course is really useful and insightful. Defo worth going on if you want to gain more knowledge or your club will pay. My club sent me so we had cover in case our 2nd team umpire couldn't do it (you lose points if you don't have a qualified umpire).
One thing that our course leader said was think how many times you've bowled (or seen it) when the batsman misses the ball and you can not believe the ball didn't hit the stumps. We've all been there, bowlers, keepers, slips even as batsmen. The ball doesn't hit the stumps that often, in fact at the standard i play i would be surprised if 5% of the deliveries bowled in the whole match would have hit the stumps.
It always has to be a case of not out unless you are totally plumb. I feel some umpires feel it makes them seem like a proper umpire to give an LBW.