Thanks a ton for your reply.
Yes. Going deeper into the theory was definitely something I was hoping for. This is a tad disheartening - also there are a few skills that I feel I am not improving on despite accumulating more dives, and I was working under the impression that the DM course would help solve for them.
The first is navigation. As a recreational diver, almost every dive is at a new site. Despite how much I try and study the dive-site map on the boat before the dive, once I'm underwater in 10 - 15 m viz, a few mins in to the dive, it is really hard to know where exactly I am and how to navigate my way around. I'm quite lost and hopelessly dependent on my DM/instructor. This is a huge gap in my skill set currently.
The second is safety, but it seems like the rescue course is good enough for that.
The third improvement area is to really perfect my propulsion techniques and buoyancy. While my trim, buoyancy etc. has certainly gotten better as I've gotten more experienced, I still look on with envy at some instructors I dive with, and really admire how elegant they look and move underwater. I tried signing on for a Peak Perf. Buoyancy course in Dahab, but they dismissed me, saying I didn't need it, and that I should just keep diving. I did do my Deep Dive and Nitrox with them though. I would however love to perfect techniques like back-finning etc. and the art of truly staying perfectly still underwater.
I am definitely keen to get into tec diving, but I'm rarely at sites that allow for tec diving, or ever visit locations where there are dive shops that support tec-diving. That's why I figured I would push it out for later. But if tec courses impart far more rigorous skill development, then I suppose that's worth considering.
I've definitely considered the GUE Fundies course. But I'm a little apprehensive of the pre-req to buy and own all the equipment. I don't live near the sea, and with a flight needed for all my dive vacations, travelling with a full dive kit just seems a little much for a recreational diver.
To clarify, dive theory, physics and physiology aren't required for PADI DMs. You could take the SDI DM eLearning. The eLearning is better coverage those topics than the PADI material I learned in my IDC.
If you want to take you diving to the next level, that's really going to be tech training.