I don't think I've ever seen someone seriously put forth the argument "all you need is Ozempic".
For context: I am an overweight type 2 diabetic. I lost about 70 lbs before my doctor started me on Mounjaro (another GLP-1 agonist). My diet and exercise routine were far from perfect, and it took me about a year to lose that weight. My doctor started me on Mounjaro, both for type 2 diabetes and weight loss. I have lost 20 lbs in about a month on it, which means I will lose three times the weight if that pace keeps up (very unlikely). When my doctor and I discussed starting Mounjaro (which the doctor suggested, not me) he made it very, VERY clear that diet and exercise were important things to work on as the weight came off.
The key there is that the pace of weight loss will not keep up as the body's caloric needs reduce due to that weight loss. So naturally a GLP-1 user will plateau if they do not adjust their diet (and potentially exercise routine, though diet is much more important) as the weight comes off. You know what really makes it easier to have the energy to a healthy meal, to work out, and to take care of yourself? Losing weight! You know what helps form those healthy habits in people who did not form them during childhood? Reduced cravings for calorie dense food! Both of those things are where Ozempic and other GLP-1 drugs shine. It gives the person on them the space to make those changes without cravings, without feeling hungry, and at a faster pace than they could do naturally.
So yes, in the short term, these drugs are a great catalyst for change, but I don't see many medical professionals saying "oh just stick someone on Ozempic for life and that's that!" because for the vast majority of people who would use those drugs for weight loss cannot achieve their goals with just the drug alone.