Perhaps a less emotive description of the changes would be that under "old" Bidline you had a high degree of control over days off, and the more senior you were, the more control you had. Yes, there was the chance of being "drafted" at short notice but there were legitimate ways of constructing your roster to protect specific days. Under Bidline as it works today you have much less control. I think the major bone of contention for many is that you can be over the monthly CAP and the company can still stick extra work on the line and/or they can shuffle trips around to generate a gap to drop work into....I'm not sure I'd describe that as "welcome to the real world", I'd described it as being stuffed.....
That said there is indeed still some degree of control. There's still the protection of non assignable days such as leave, and as a back stop the possibility of swoping a trip with a colleague to generate a gap where you need it, however that is becoming increasingly problematic due to everybody's workload and will become even more difficult under EASA.
Ultimately if you join BA in the knowledge that in a month with no non-assignable days (e.g. leave, Duty Free week) you have no guaranteed choice or clarity as to your days off until final rosters are published you'll handle it fine.
...and that's all I want to say about that...
