So how does the body start producing testosterone naturally again if lh and fsh levels could be completely tanked? You sound like you have don’t a few cycles in your day, did you do no pct on your first few and do you still not do them? Or the more you do the less likely your body to naturally rebound?
The Hypothalamic-Pituitary-Gonadal Axis (HPGA): The GNRH is produced in the brain and stimulates the production of LH and FSH, these then stimulate Leydig cells in the testes to produce Testosterone. Now, here is the feedback system: test aromatizes into Estradiol which goes back to the hypothalamus in the brain and INHIBITS GNRH. More estradiol=less GNRH. At this point, it is important to note that DHT (also metabolized from testosterone) ALSO inhibits LH/FSH production at supraphysiological levels (i.e. when taking testosterone).
So, understanding the above, let's break it down: when you are shut down, GNRH is off, LH/FSH are off, and Leydig cells aren't being stimulated to produce testosterone. This is believed (maybe proved) to cause a decrease in the number of Leydig cells. Your brain can still produce GNRH and LH/FSH, they are signaled to be off from an abundance of Estradiol and DHT (anything DHT does other androgens probably also do to varying degrees btw, but this isn't important).
So, what is the perfect environment for post cycle recovery? Conditions that signal GNRH and LH/FSH to turn on: Low Estradiol and low DHT (androgens), low E2 (estradiol) being the most important one.
What can be a hindrance to recovery at this point? Lost Leydig cells from being on too long. What is the solution? Some doctors have suggested "keeping the horses in the barn" by doing very low amounts of HCG during cycle, this is usually in the range of 200-500iu (250iu is common I think) once or twice a week. HCG mimics LH/FSH and will stimulate Leydig cells and theoretically keep them around (zero proof or studies on any of this, but the logic is sound). While this is somewhat effective, HCG can be expensive (because of that dumb HCG diet omg) and HCG is "estrogenic" (one of my favorite TRT docs likes to say).
Now let's talk about the problem with "PCT." Nolvadex blocks estradiol receptors, this tricks the hypothalamus into producing GNRH, which will then stimulate LH/FSH (as long as too much DHT/androgen isn't present), this then stimulates Test production and that test aromatizes into E2, but that E2 has the same problem, it can't (negatively) stimulate GNRH because of the nolvadex. Now you remove the nolvadex and instantly have perfect conditions for shutting you back down: high E2. Clomid works in very similar way, and it is important to note that clomid has E2 blocking metabolites that stay in the body for up to 6 weeks or longer (hasn't been researched but there are case studies on it). HCG mimics LH/FSH which stimulates Test production, which aromatizes into E2, which shuts down GNRH and LH/FSH. HCG is NOT a tool for recovery as you can see, it just keeps GNRH and LH/FSH turned off.
Now you can see the problem unless these PCTs are somehow fixing the Leydig cell issue (which is highly unlikely), they are just going to keep you shut down longer, but if you are jumping right back on cycle after a few months, you will probably never notice that your PCT didn't work, in fact, your PCT will just be a bridge between cycles to keep test high (probably supraphysiological also btw, easy to do with these drugs).
Now with the understanding you have from the above (and if you got all that, you now understand the HPGA better than many doctors), you can try to create the "perfect recovery" conditions: You are coming off cycle, androgen levels are falling, estrogen is probably going to be high, you may want to 'control' that estrogen as androgens levels fall so that you can reach your goal of LOW TEST and LOW E2 evenly. You don't want to spend a bunch of time at low T and high E2, this will delay recovery. This could be as simple as taking a little nolvadex as your esters are clearing, with the goal of having the nolvadex out of your system at the same time as your T levels are getting very low. You may also want to do what you can to keep Leydig cells around, this could be HCG on cycle, or better yet, just don't stay on cycle forever, come off, let your body recover (hardly anyone actually does this, turns out AAS are super psychologically addicting also).
One further word regarding AIs, while they seem to be somewhat of a solution to a lot of this, they really are not. Unfortunately, AIs cause (and this is in the words of an endocrinologist) "hyperactive aromatase" and there is no reason to think suicidal AIs offer any protection from this (old broscience rumor that has really taken hold as of late). Also, while AIs can lower E2, they will stimulate Test production which will raise androgens and can shut down LH/FSH.
A bit of personal broscience: I think that reductase (that converts Test to DHT) also becomes somewhat 'hyperactive' on supraphysiological of androgens and that this can delay recovery via the androgen feedback pathway, a little finasteride while esters are clearing may help with this.