Disclaimer: This post may qualify as a bunch of ramblings
Lessons have helped me immensely and I'm hitting the ball better than I ever have before. It has been fairly costly, but my swing was so fundamentally flawed and my knowledge and understanding of it so limited, that I was never going to get any better - and I had tried! For someone like myself or a beginner, I think lessons are a no-brainer and almost a must. In such cases the overhaul or a specific swing philosophy is probably needed. but for others (like some of the commenters here) who are low handicaps, what is needed can be drastically different. The last thing i would want now, is to start over with a completely new theory/philosophy and I'm not a low handicapper yet. It just takes a ton of work! Whatever my ceiling is with the track I'm on now, is going to be my ceiling.
When an instructor wants to make every golfer adhere to his swing philosophy, I think he/she may be missing the mark in not knowing/caring what the golfer actually wants out of his game. Certainly any scratch player is going to need a very compelling reason to make drastic changes and any good instructor should carefully weigh what instruction is given to someone at that skill level. On the flip-side, if the golfer (like me) says the goal is to get to scratch, but my fundamentally flawed hack attack (I wouldn't call it a swing ) was never going to have a high-enough ceiling to allow me to get there, so I had to be willing to make drastic changes and to put in the work - lots of it! Probably more work than most beginners, because I had to undo the years of bad habits. I think lessons for someone who has the swing they want/need, then any instructing should be about tweaking and understanding nuances, not a major philosophy shift and overhaul.
One more thing, in my work (financial advisor) I've had to realize and accept/embrace that I may not be a good fit for every potential client. Things like communication style, personality, and experience (among other things) can all make us better suited two work with certain types of people and/or companies. I think golf instruction is no different. We may have a hard time "hearing" what one instructor is saying (or him understanding what I want) while we almost immediately "get" what another instructor might say, even if they're trying to convey the exact same concept. All these things can factor in, and like so many other things in life, it comes back to relationships, comfort level and trust. If those aren't present, I'm not going to be willing to commit to a whole pile of work for something that I'm not sold on.