I think people are vastly overrating the value of pick swaps. Could you end up giving up the #1 overall pick? Sure, it's theoretically possible--it's also theoretically possible to trade CJ for Giannis and end up regretting it if Giannis suffers a career-ending injury the next day. You don't value something by the worst possible scenario you can construct. The expected value of a pick swap, especially years out, is pretty close to 0...the further you move from the current situation, the likelier it is that both teams are somewhere in the middle of the draft. When the starting point for both teams (considering the 76ers will be losing one of their two regular season stars) is already probably around the middle of the draft, that's even more true.
Could the Blazers lose Lillard and end up tanking for several years? Yes, that's possible. It's also possible that Simmons elevates them and they're an easy playoff team for the next four or five years, nearly assuring that those pick swaps are valueless. I think the second scenario is likelier than the first.
Pick swaps are so popular because rules prohibit trading more first-round picks unless you want to go something like a decade into the future (you can't be without a first round pick two years in a row) and so swaps are the next level of draft capital--but they're lottery tickets, not highly valuable assets in and of themselves.