At first, it did seem cool, and it did start off being fun as the new chapter started, but... building needs to be back, and without a non-building mode.
I'm not exactly building huge forts in seconds like "sweats" do, my building is decent. I can put up a wall here and there, and have always more relied on shooting. But building is resourceful and not just for protection or cover, but for getting places quicker, if you're in the storm and need to put stairs down to get up a mountain.
As for "sweats," I play on Xbox, and will probably come across 1 to 2 really sweaty people and it's not even every match, more so every couple of matches. I think the only time you're gonna find a lot of sweats is on PC. Console is much calmer.
Now if they do add a separate mode, that will give the opportunity for more sweats to join a regular building mode, not all of them are just gonna hop into Arena. Of course, I do think there will still be players that do okay with building that will still play the building mode, but jumping in and playing against players that have a diverse level of skill is what makes it balanced. People are making it seem like there are sweats at every corner when it's not the case, at least on console.
I gotta be honest, hearing casual players that are coming and saying Fortnite is better without building or players that stopped playing a long time ago saying it's the most fun it's been in however long sounds a little ridiculous. The game has been fun for a while, sure some seasons I didn't like, but it was still fun.
Everyone's saying people can't hide behind their builds anymore, and I get it. But I haven't been beaten by every sweat I went against. Again, I'm not great at building, but it doesn't hurt to learn. My building is way better than it was before, yet I haven't gotten close to doing quick edits yet. I get some people like no building, but a lot of it is just casual players wanting an easy win. If they do add a separate mode, I hope that it will just be for a while, but I prefer they don't.