Actually I really like UV resins- I've tried most of the brands on the market, and use them a lot for certain things. Any time I want to replace epoxy as a head or body material, for example, light cured resins are the obvious choice. They are cleaner, consistent while working, set up instantly and don't yellow. But there are also things that they don't do better than the materials we had before. They're not glue and it doesn't matter how many people call them glue. If you need an adhesive an actual glue is the way to go. When it comes to finishing the heads on trout flies they're not as good as varnish. Yes they cure quicker, but they don't really speed up the tying process. Who is sitting with a fly in the vice waiting for varnish to dry? By the time I'd have picked up the torch and cured the resin I've already started the next fly. Not only that there are often problems with resin delaminating from the fly. I've researched this and there seem to be either 1 or both of 2 things going on; first could be the resin is just sitting on top of material and easily gets lifted as water gets under it. Second is that the thin resins are soaking in but aren't curing under the layers of non transparent thread(no coincidence that it often happens on black buzzers) which allows the acrylic to rehydrate allowing it to come free. Varnish is cheap, cures regardless of how deeply it's absorbed by material and isn't really slower for most trout or smaller flies. UV acrylics have revolutionised certain aspects of fly tying and fly design, but they don't do everything.
I feel basically the same about super threads, power silk and nano silk. They're great for some things and I'd never want to go back to tying bass bugs with 3/0 or kevlar. They're tough making them perfect for flies for toothy predators like pike and musky. Although I tend to use them in 150 den 6/0 size for these so the incredible thinness is not really that important here. For many it seems that the fact they can tie with 18/0 thread and not worry about breaking it is apparently a boon. I'm not really sure why, except for say size 20 and smaller flies where the thread is in proportion to the hook size. The main comment I hear about them is that you can put lots of wraps on the fly and not get bulk. What I can't grasp is why you would want to! Far better to learn good thread control and make the turns you do put in count. In most situations 3 good turns of 8/0 is enough to hold any material with a few more offering perfect security, not so with slippery 18/0; pull too tight and you might cut the material you're trying to secure not tight enough and you'll need loads of wraps. So it's more work to fill the hook, tying in is often slower and you need more of a more expensive material. It's probably no coincidence that semperfli followed the nano silk range with a range of more standard waxed threads once they got their name out.
Lots of new things are really cool and can offer a lot to the tier, just because something is useful for one thing doesn't mean it'll be the best for every application. If you only have a hammer, every problem starts to look like a nail.