Can, not will. You're right though to point out that the body loves homeostasis and will downregulate endogenous testosterone production if serum levels are high from supplementation. Testicular atrophy from extended use is a real potential problem.
Unfortunately, TRT clinics are like the Internet Viagra doctors: they are drug dealers with an MD.
If you have low testosterone then see an endocrinologist or a urologist for treatment. There are certainly cases where exogenous testosterone injections are indicated, but depending on the kind of hypogonadism in question there can be better alternatives that don't involve injections or infertility.
It's worth noting that the secular testosterone decline is not a "new normal," but rather basically every man in the West is suffering from some kind of hypogonadism. We can speculate about the causes, but the precipitous drops in average population serum testosterone levels measured over the past decades is anything but natural or normal.
> many of which are long lasting or permanent
True, but not all of the permanent effects are negative. Exogenous testosterone causes muscle cell nuclei to multiply, and there is a permanent anabolic effect as a result. It's nowhere near as dramatic as being on exogenous androgens, but it's still significant.