Based on the context I assume you are talking specifically about BA rather than about airlines in general. Assuming you're talking specifically about BA, your comment about fish is one thing I completely disagree with.

I used to avoid fish on all airlines after encountering far too many dry and overcooked fish on QF, but I decided one time that since there were so many grumpy people on board (this was in CE) I asked to be served last because I could no longer bear the grumpiness exhibited by some passengers towards cabin crew members. I thought at least there would be one fewer complaining grumpy person from missing out on their preference. As it turns out that was my gain. There was only fish left so I had it, and to my surprise it was neither dry nor overcooked. So, that was my first encounter with a fish dish on an airline for a long time.

I have since then been having fish as my preferred meal on BA, but not on other airlines (I have tried them since on other airlines and they were dry). This is one thing that BA somehow do well in my opinion. I have had dry chicken, dry duck and dry beef etc, but I have never had BA serve me dry fish yet, except just once, out of SEA in CW, which caught me by surprise. I was so surprised that I still remember it. I find fish to be the "safest" option on BA after hundreds of sectors.

As for beef, as long as it is braised, I have never had a problem - not exactly difficult because if it's properly braised, it is not possible to make it tough by reheating. I normally avoid non-braised beef but did take a chance with beef (the salad version, so no reheating was involved) and it surprised me that it was nice.

I'm a little bit surprised at your comment that "even chickens can be overcooked and dry" though. Chicken (in particular breast, legs are generally safe) is the dish that is most prone to being dry because chicken breast is a bit dry to start with. Chicken breast is something I do my best to avoid whenever I can on any airline, including BA. The number of dry chicken dishes I have had (including on BA) have put me off.

Having said all that, I agree that BA's F meals don't generally qualify as "fine dining", particularly the main course.