In addition to RaiderDawg comments, I'll add that Kermit was also vocal in radio interviews about a down year and needing to rebuild this upcoming season. While those comments can't be found via search, he certainly said them repeatedly, publicly, and openly even before the end of the season.
While there are not impressive stats for Simpson such as ppg to look at, he may have been the team's best defender which is why Kermit continued to giving him playing time despite his lack of big offensive output. It's not accurate to just dismiss Simpson as irrelevant or some such thing.
At the high level MT has climbed over the years, not having a big man already on the roster to replace Brandon Walters is a setback. As much as I like Gamble, he has not shown dominant play yet in his career. He has improved some over the years and has good athleticism, but I doubt he's a full replacement for Walters.
On top of losing your team's best defender and senior leader, losing two senior all conference players including the C-USA POY is a huge loss that is really difficult to replace...for any team. Maybe Kermit could have landed another grad transfer, maybe he couldn't. Even if he did, there aren't any guarantees that they would have been as highly successful as recent past examples. Frankly, I find it pretty amazing what Kermit was able to do with those one year transfers.
All of this did not or does not suggest MT will "suck" this upcoming season. It's possible they could still have a good season. Maybe they do tank with all the changes. Whatever the case, it's not a forgone conclusion that this team will be some walking disaster this next year.