True, true. You can fashion a mech out of anything if you can't find a purpose-built one. Those things are apocalypse-proof, though.
That aside, I think they're great as learning tools. I think every vaper who wants to tread the deeper waters should start with a mech rather than, say, a Sigelei 150.
It's sort of like how when you start studying photography, you use a basic and dated, 35mm film SLR instead of a digital SLR because it forces you to learn about what goes into making a good photograph and how a camera works and yet it's harder to break, but you're still working with a very powerful and flexible medium. Everything you need to make professional-quality art is there... ...somewhere.
You learn to do things for yourself that other cameras can do for you because you can't even see the pictures you're taking until you kill that roll and develop it, and that puts you at an advantage when you get one with more advanced features because you already have that fundamental understanding of how and why they do what they do, so you can take full advantage of the power they put into your hands. You already know how to meter on the fly and adjust shutter speed for your film to get the proper detail/exposure. "Auto-focus" only saves you a bit of trouble. If you know how to operate a 35mm film camera well, then the rest are toys to you. You could build one yourself, if you needed to.
The more you work for it, the more it works for you, yanno?
The same goes for mechs, really. If you can learn to get what you want out of one, then the world of vaping is yours.