I hope so as well, but experience has taught me that no first gen version of any car has ever been even close to "perfect", and certainly not in the long run. And it's not just potential reliability issues. Build quality, available features, everything evolves, and with a BEV, ever so quickly.
I take the 2013 Model S I drove back then and compare it to the 2016 one I drove a couple of months ago. A world of difference, the current one was better in every aspect, every one. And even since then it has evolved dramatically. Facelift exterieur, AP 2 hardware, to name but two aspects. Now imagine my prospective 2018 Model 3 versus a 2021/22 one. Going by the experience with Tesla over the last few years would expect the latter to be so dramatically better that the former pales in comparison in almost every aspect also.
I disagree. The reason Model S is so different in three years is because Tesla's EV tech was brand new and still developing. Hell, we didn't even have AWD on the first models! But the rapid development of new core features is over. There really aren't any more radical changes to expect and that's why Tesla is now focusing on the 3: to take what they learned and developed and make it cheaper.
Especially in a car like the Model 3, the R&D is mostly over. There will be no major changes in the next 5 years for the 3. Hell, we even already have full self-driving hardware. Battery tech is pretty much maxed out according to Elon. Looking at the differences between 2013 and 2016 Model S, what comparable hardware changes can you possibly envision for 2018 vs 2021 Model 3?
One of my big concerns with an early Model 3 would be that AP hardware would undoubtedly improve a few years later. This is no longer the case which greatly improves my confidence in buying a new 3.
This all said, I agree with your statement that no first gen car has been anywhere close to perfect (except maybe the Prius, damn what a well-designed car) and the Model 3 will be no different. There will be problems, but one can hope that Tesla's decade of EV experience and development has come close to plateauing and we will see solid cars from here on out. Major changes have been made to the drive unit in the past year or so and reliability concerns have greatly dropped off since then. All that's left is fit and finish, really. Software gremlins too, but those will always be problems with Tesla until they are comfortable enough with the drive hardware/software to focus on comfort.
I'm nervous as hell about purchasing a first gen 3. I want the car soon because my current shitbox is on its way out. I also don't want to lease because that'll end up being far more expensive than buying and I'm not convinced the 2021 Model 3 will be so outrageously better (see above) that I'll regret buying early. Also, leases suck for a ton of reasons. This will be an insanely fun car to drive and I will likely take the long way home more often than not. I never want to be in a position where I have to budget my miles or be afraid to drive the damn thing.
Solution: get the ESA and have fun for 8 years. I may be taking a few more trips to the service center in the car's later (and earlier) years than the 2021 owners, but I am reasonably confident that the 2018 Model 3 will be competitive for years to come.