I definitely believe lunging has its place in my training. For me personally, it has always been there to help with my green horses, teach them jumping and then let them jump (I don't jump now but as a kid I loved to haha), work on voice commands, check for their energy levels/any stiffness or sound issues, etc etc. Recently it has become an essential tool for me to reintroduce to both my horses as I broke my leg last year and can barely ride. Spring is on its way here in NZ and I'm already plodding around on one of my horses, but lunging helps her maintain a low level of fitness when I can't ride. It also is curing the boredom in my gelding, who I can't personally ride anymore, and is waiting for better weather so he can be put back under saddle by a friend and sold on. My horses personally enjoy it. And we don't just do circles either - I make a point to walk out wider with them to use all our space, and working on lengthening of stride by making an oval and pushing them on the straights - they love it! I've never found muscle soreness in either of my horses from lunging frequently either. My instructor has cleared me for 3 sessions of no longer than 20mins each week with my horses, albeit with it being winter I've yet to use all three a week. With the ground firming up however, I will and have no issue with the remarks I get from others either. Some people just have to do what they do, and its just a tool I believe in. There are certainly many methods of riding/handling of horses that I don't necessarily believe in myself to be beneficial, but like the OP said, each to their own and only share your opinion if asked.
Great thread, was a good read :)
♥ Seoul Searchin' for the Lovebug ♥