The "match the hatch" crowd has it's work cut out for it. In order to tie an exact replica of a mayfly, caddis, etc, you first have to study the actual bug very closely. It's not enough to completely know what every part of the insect looks like, you must also have the fly tying skills & knowledge to actually make a perfect (or near perfect) re-creation. Depending on the level of detail you want to accomplish with your imitation, it could a lifetime of experience & practice to get your fly the way you want it. This is not to mention the availability of tying materials, etc.....
On the other hand, the "as long as it fools the fish" group of anglers simply tie up a box full of different patterns at the bench while relaxing & dreaming of their next fishing trip. Sure, they've practiced tying these patterns & are quite skilled at making them. Yes, they've studies the natural insect's behavior & learned how to impart that behavior into their imitations. But have they studied magnified photo slides of a particular insect? Looked at it under a microscope? Raised a family of them in a fish tank from egg to spinners? No, they haven't. Nor do they want to. This group is quite content with the contents of their fly boxes, thank you very much.
So, is one of these two schools of thought taking a more correct approach to the sport & therefore better at it? I don't happen to think so.
In my personal experience, I've tried both approaches & had enjoyment while fishing either way. I tend to lean more towards the "casual imitation" way of thinking about flies, but I blame this on my general lack of fly tying skills. If I had more time to devote to practicing fly tying, I'd get better (hopefully). Since I don't, I'm happy that the flies I tie are just good enough to get the job done (again, hopefully). Still, there are one or two specific hatches on my local streams that I do go to the trouble of matching as closely as possible, but I don't have the skills to do that all the time.
In the end who's happier, the general or the exact imitators? I guess that depends on your personal disposition & which aspects of fly fishing you most enjoy. Either way that's the point isn't it: to enjoy the sport? I say follow the school of thought that makes you happy!!