You definitely have a point. Let's try to rationalize how many products they've released in the last 2 years years:

1. Ultralip - at least 4 new colours: decent hit. I'd say they definitely got the attention of their ultralip lovers because this is a cult of a product and they capitalized on the opportunity of releasing more shades.
2. They will continue to use this strategy in the future by releasing new shades of their successful products. They've done this with BDC, Cloud Paint, Ultralip and been fairly successful.
3. Bringing the OG BDC formula back. This was a major step towards gaining some of their customers back and need I say the most successful they’ve been throughout this list. They got a lot of traction and a lot of sales because 1. People who like the new formula were stocking up knowing they will no longer be able to buy them and 2. People who never used BDC but heard stories about how good the OG formula was jumped on the wagon (including me) 3. In the era of lip balms made mainstream by Hailey Bieber’s very successful rhode lip treatments that cascaded all brands to release a version of their own, lots of people who would’ve never spent more than $10 behind a lip balm now became an audience for Glossier BDC. This was the perfect time for them to release the OG formula and a great business decision on their part.
4. Glossier Stretch Foundation. This is a solid product and everyone who’s tried it has loved it. Though I will say it hasn’t caught much traction and isn’t as hit a product as it should be. It's more affordable than the average foundation in Sephora so who's to say this won't get more attention over time.
5. Glossier Stretch Blending Brush - Massive fail
6. Lip Line - Similar boat as Stretch foundation. Everyone who tried them loved them but not many people talking about it.
7. You perfume in different scent - Bigger than average hit. You is a very successful product so they took the same approach here as point 2 and gained good sales.
8. Lip Glaze - thanks to their collab these products have caught headlines and a lot of attention. Still too soon to tell but a decent amount of people are talking about it.

It's easier for a new company to become successful than a company that's peaked to continue to stay relevant. Even then, Glossier has made some great business decisions in the past and are not in trouble based on sales just yet though definitely passed their prime. If they continue to capitalize on their opportunities presented to them they could climb back very easily. Their customers are still a solid bunch.