My advice to hold pool swimmers would be to get your foot in the door and your name on the seniority list, then worry about your fleet later (if it's not the one you want from day one). Nowhere's perfect, BA included, but if you're joining for a specific fleet then you're missing the big picture of what BA offers.
Just to add to what Bex has said above, if you don't like the way BA does things then don't apply. It's a big seniority machine where the computers have names and the people have numbers. But despite its downsides, BA is still better than most airlines out there. If you don't agree then save your days off for something more pleasant than computer tests and interviews.