I know it's an unpopular opinion, but Keaton was never really that believable for me as Batman.
Never bought into Keaton either. Batman as a pudgy middle-aged man? Yeahhh... Sorry don't buy it.
Blame Tim Burton, with his insecurities about strong male figures. In fact, during a Today
show interview during the 1989 film's week of release, he said he was avoiding the "square jawed" type of person. Major personal hang-up. He thought Batman was just a "geek" with high tech gadgets/suit.
It is no wonder his films have not stood the test of time.