I think it's pretty telling that the MOS and 19X are the most recent Glocks to get people excited. The "tactical" market is huge, and Glock only seems to cater to it every once in a while.IMO, they should have stuck with the gen 4, maybe added a couple other variants
Here are what I would consider mistakes:
1. You can't even buy an MOS with a factory threaded barrel.
2. Phasing out the C models without trying to replace them with proper carry-comp models.
3. Not trying to make a full-size single-stack gun. Given how many shooting sports are limited to 10 or 8rd magazines, I genuinely believe something like this could sell well.
ETA: to be fair, the single-stack guns were pretty well-received and had more new bits, so credit where credit is due.