Eeek, you asked the question, expect a mountain of responses.
Just remember that we all joined at different times, many with very different expectations about what we wanted from a career. When I joined, all the JOs wanted to serve to 55 and get a star, now things are very different at a military career is sometimes seen as a stepping stone to other things; people do not necessarily want a PC anymore.
Things change that impact how we look at ourselves and what we want from life and what we are prepared to accept. Changes in conditions and opportunities will affect us all differently and when we say 'it is not the Service we joined' that is because it is not. But it WILL be the Service you join, and if you go in with your eyes wide open and an open mind you can get what you want out of a career. How you react to changes that occur in your time will decide what your view will be.
It is normally the most opinionated of us that post on this forum, so there is not a lot of fence-sitting; bear that in mind when judging posts. There are a great many Service personnel living contended lives and enjoying their jobs, albeit with very different ambitions to those that went before. Evolution, it happens.