How many users are using browsers that are old enough they don’t even support JS? It’s one thing to disable it for security/privacy (which the OP was talking about), because those users are probably more tech savy.

Do these old browsers not support DuckDuckGo?

Unfortunately, unscrupulous companies can build shadow profiles that bypass cookie and storage based isolation techniques like this.

Your browser gives off a lot of information. See here for some of the information they can use: https://amiunique.org/

You’re best off blocking things with uBlock Origin vs something that just isolates.