This also happens with me. I'm definitely capable (and have a couple of times in the past) of losing weight long-term (longer than a few years) by continuing to eat less healthy food, but less. I've eaten those foods all my life, in fact, and never been at all overweight. You can achieve significant, sustainable weight loss on a less healthy diet.
The trick that gets people, I imagine, is that you really can't eat very much of it all, especially as I've gotten older. You have to be willing to eat rather small portions, and rather infrequently.
I do imagine it will get harder to deal with the "density" of processed food as I get more fit and closer to ideal weight, because calorie dense foods will hit the limit rather quickly.
Thankfully, I like plenty of non-dense foods too and can adjust the balance without cutting any desirable foods completely
The trick that gets people, I imagine, is that you really can't eat very much of it all, especially as I've gotten older. You have to be willing to eat rather small portions, and rather infrequently.