If you only move lower level prospects, you're only going to get a low-level return. You can't be afraid to move someone with actual upside because that's what it takes to get valuable pieces.
Not doing anything in the offseason was a blunder because now the trade market is basically frozen until July unless you overpay. And anyone you get will only be there for around 1/3 of the season. Huge missed opportunity.
There is also positional scarcity in MLB that you have to factor in. Groshans is going to be a 3B, which is good, they need a 3B on the team. But so is Austin Martin probably. so is Miguel Hiraldo. Orelvis Martinez might stick at SS but even he might not. Kevin Smith looks like he's a prospect again, and he plays SS/3B. You could probably convince Semien to come back and play there. So dealing Groshans depletes that position less than you would think. Even more likely is that he never makes it. Just one example but he probably would have been worth a very good young SP in the offseason, and they had an enormous hole there.
I wouldn't trade Austin Martin. I would have never traded Vladdy or Bo when they were prospects, but aside from the guys who are as close to sure things as prospects get, everyone should be on the table once a team moves into the contention window. Jays probably aren't there yet, but they seem to think they are.