some shuls have very specific minhagim they are makpid on, and 90 seconds before the time for davening is not enough time to go over those minhagim. where i daven for example, they are makpid on specific pronunciation certain words (morid hageshem not gushem, for example) among other such examples. therefore they are comfortable if a “regular” gets up for the amud and not someone unfamiliar with their various hakpados. it is easy to label a minyan and say its members lack ahavas yisrael, but it is equally a lack of ahavas yisrael when one simply doesnt consider there is another side to the story and comes to erroneous, and worse, spurious conclusions.
