For most of its history, the prime building block of Second Life was the prim. It wasn't particularly hard to figure out how to make one nor how to shape it and connect it to others to build an object. If you spent a few hours a day teasing prims, you'd probably at least learn to build a simple house in a week.
Of course, you needed to texture it, but that wasn't too hard, either. Select the surface, add the texture. There were numerous free textures covering basic surfaces; so again, you could in a week learn to build not only a house but make a brick house with asphalt roofing and wooden panel floors. It wouldn't be the prettiest house, perhaps, but if one kept at it, you could gradually get better and better.
If you needed a custom texture, you needed to import it. But this task was not that hard, either. It only cost L$10 (that's what? A few cents in RL money?) to import one picture, and most people have photoshop and everyone has MS Paint. The Lindens even offered templates so you could create clothing textures. It was never difficult and the most expensive part was the L$10 import fee.
Then along came sculpties and for the first time, it became harder to be a builder. You could still work with prims, but sculpties required being able to work in Maya or similar programs, programs less commonly seen to the average user. You needed these programs because the sculpty shape was read from an image, which has to be crafted just so to create the correct shape. And to color that image, you needed the same program to export the color layer. You had to create a unique texture for each unique sculpty.
And there you go. Suddenly, it became harder to enter the building market because you needed a sculpting program, and learn how to use that, and learn how to use SL's building tools on top of it all. And you came to need a minimum cash investment. Prims and prim textures are free, but even if you use free sculpting programs, the texture import fees would be at least L$20 (10 for the sculpty base and 10 for attending texture).
That's not to say a new builder can't get a foot in the door, but it's much harder. Sculpties are part of the standard now. People are prim aware, and a choice between a 1 prim sculpty staircase and your 10 prim one... they'll spring for the former. Plus, a sculpty will usually look more natural and less chunky than a similar prim object.
I haven't done research, but I wouldn't be surprised if we lost something in the leap to sculpties. You can't just 'leap in' anymore, amateur style, at least if you want a serious business. And I think people do want a serious business. They want others to look and praise their work.
And now, with mesh, I'm not sure what to think. It's still kinda sorta new, and I don't think it will have the same impact as sculpties, mostly because sculpties already broke the ground on shifting building from an inworld enterprise to an import one. That's a shift I'm not sure was good for the world. Especially when it's expected. You come in expecting to be able to build your world, and then are told you need Maya and all manner of other external programs... It discourages some. It also hobbles teaching. I can inspect a prim structure and point out how to fix it or make it better. With sculpties or mesh, I'd have to send them out and rework it.
And it's being used to divide the world as well, or so it seems. Only the new viewer can see mesh, so you're outta luck if you want to stay on the somewhat more stable old viewer. Heaven help you if your computer isn't too fast, either, because then sculpties (and I presume mesh as well) will turn up as odd spheres, which morph into these twisted piles of wire before finally settling down into the actual object. It's ugly.
I will not doubt that sculpties (and possibly mesh) have made our world a little more beautiful. But it sure is a shame the cost is to essentially outsource building tools offworld and beyond the reach of most of the grid.