first thing: Brogdon was not the future so yeah, no upside was lost by trading him. However, he was the best player on the team statistically. There's also this: Portland won 15 games when Brogdon played; they won 6 games when he didn't play. A .380 winning percentage when he played; a .140 winning percentage when he didn't. He was the most impactful player. Obviously, there was more going on than just the Brogdon influence, but having a savvy veteran who actually knew how to run an NBA offense vs Ant and Scoot, who didn't, was a big factor
as far as the two draft picks, we don't know how good or bad the 2029 pick will be. Hypothetically it could be the 2nd pick in a great draft, or the 30th pick in a poor draft. Just going by where Portland and Milwaukee are, and where they are projected to be in 2029, there is certainly some risk in giving up one of those picks (I'm assuming the Celtics will still be good). Blazers also traded two 2nd round picks, their own in 2028 & 2030. One final note: when the Blazers fork over that future 1st, it could be a year after Avdija has left as a UFA.
whether or not it was an overpay is probably going to depend on how good Avdija actually is. It was a steep price though. For certain, trading away two first's (#16 & #23) for Covington was not a good deal for the Blazers. Avdija looks like a more complete player, but he really only had 1 solid year out of 4 on a bad team