@Stas_Gorelik Just so you’re aware, I can’t see what you see, and I don’t work for Netlify, so I have precisely zero visibility.
I’m just providing guidance on what “might be wrong” based only on your explanation, and issues that I’ve seen others experience over the years. So I could be wildly wrong on my guesses.
The “Drag & Drop” system is fairly simple, but it is also ‘error prone’ and Netlify don’t plan on fixing it, as it’s not a primary method for site creation/updates for them, it just exists for people to “try things out”, see this thread:
https://answers.netlify.com/t/fixed-drag-drop-issue-status-workaround/64314/18
You simply shouldn’t need to delete the existing site to upload a new version of it.
Either to the existing site, or to a new site on Netlify.
But at this stage it’s also unfortunately ‘less likely that something is wrong on Netlify’ than 'you’re just confused or making a mistake somehow’.
So I’m advising from that perspective, trying to get you to just look at your files, the relevant documentation etc. If we started seeing others report the same issue in a short time-frame, then I’d start to lean towards there being some actual issue.
If it’s at all possible, you should switch to using either git deployment or the CLI.