I think there are two separate conversations to be had here. Did Grier do a good job with the tear down and obtaining draft picks for players we were jettisoning? And were the players we selected successful? You might add... was he successful when he was attempting to work with previous coaches... but I'll leave that one alone for a bit.
The answer to the first question really can't be anything but yes. He blew up the roster in a way that few teams have ever done, and in so doing, he netted so many picks that we controlled the board in 2020 and again in 2021, and gave the Dolphins tons of cap space. Space, we used to bring in Jones, Lawson, Ogbah, Flowers etc.
The second question is trickier... because people want to blame him for moves made when he wasn't fully in charge... I'm going to reject that, and just look at '19 and '20. Thus far, the '19 yielded only one real clunker. Prince... a 6th round project that we quickly soured upon. Dieter might be a miss, but it is still to early to say for sure. The rest of that draft is looking pretty good. Wilkins is rated as one of top 5 run stopping DTs, Van Ginkle is REALLY stepping up after an injury plagued rookie season (and as a 5th round pick too), Gaskin has become our starting running back from the 6th round, and Cox has been a nice blocking back with that forgettable 7th round pick. Not bad... no great stars yet, but Wilkins and Van Ginkle sure look like they are going to be pretty damned good.
In '20, Grier beefed up the scouting department... something a competent GM does ... and it looks like we've struck gold. I won't recount these players... we all know them.
So what I'm left with is that many posters want to blame Grier because he was part of the equation while trying to work with a coach who we all now see is incompetent. Trying to work with Gase and give Gase the type of players that he wanted didn't work. That said, some decent players were drafted in 17 and 18. Jason Sanders, Smythe and Gesicki... Baker, Minkah (spits), Godchaux, McMillan, Ford... Were these drafts great? No... but they weren't as bad as some claim. Yes, Charles Harris didn't work out, and no, Minkah couldn't learn to act like a grown man, but these players have proven to be NFL caliber players.
If you look around the league and check out what other teams have done, you'll see about the same ratio of hits to misses that Grier managed in his first couple of years on the job... and that was as a new guy dealing with an idiot coach. I just don't understand the Grier hatred and just chalk it up to rank impatience.