Yes, it might seem to you everything around you turned into mesh. But then again, it all was mesh from the beginning. A prim is a mesh, every avatar was always a mesh. The viewer is build to interact up to some point with mesh. You can use the sliders to change the looks of your avatar. That works for the user made mesh bodies too. Up to a point ofcourse, every software and platform has it's limits and they always will. That never changed. As to editing meshes that are not avatars, you can edit them. Resize, rotate, move, just like any classic prim cube can be edited. How much you can edit them is up to the creator. Just like it always was from the start.
I really like this part
i notice,they change the starting avatar,but the default body and shape are still the same..
as none of those mesh avatar are mod,or can even fit together,what is making all those mesh worst than ever,
keep in mind this is my opinoin nothing more,
i will keep build whit the inworld posibility as i like walk in it and make script(basic),
and if you see a prim avatar scripted it me