It is not ineffective outside of clinical trials. All the evidence says that people gain some weight back after they discontinue treatment - which is not a lack of efficacy. But they also usually gain back less then they lost.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12361690/

It's kind of two separate topics: 1. Whether patients can adhere to GLP1. 2. Whether discontinuation leads to weight regain.