I find the absolute dismissal of this concern by so many to be pretty telling. If there is an issue, that would likely be why it has continued. The type of customers apple wants are the ones that would never even entertain such a thought. Jut the number of issues that arise from each update is worrying enough, I can understand with PC considering there is almost infinite configurations, but due to apple's serialization and proprietary disposition, the possible configurations are EXTREMELY limited, so why so many issues?
I digress, though. I have never had a brand new Apple product except for the iPad I got my daughter for her drawing. I have however worked on many and used them for work and had many given to me "broken" or because they are "too old"(aka 3 years old). I have noticed considerable issues with performance after "upgrading" MacOS. I first noticed it about 8 years ago or so with a 2013 13" Macbook Pro. It was only a year old when I got it from work. it worked just fine for a while. I never added any software to it and all of the stuff I used for work was cloud based via a browser. However after a couple years, it started becoming more and more useless as updates were applied and especially after going to a new OS version. Nothing changed with the programs or use cases, but things started taking 5x as long to open after clicking, etc. I upgraded the RAM to the max capacity at the time (only 8GB) at the fastest mhz it could handle. I also spent WAY too much for a Mac compatible SSD. Still, ZERO improvement! I actually stopped using it and went to using an old Acer I got in like 2010(w/ Windows 7 installed I believe) for $300 running the newest version of Windows 10 at the time, instead and it was lightning fast in comparison using the same programs. I finally broke that Macbook back out in like 2018 to see what I could use it for, but it would not work at all really. It would boot up and get to desktop eventually, but EVERYTHING I tried to do would time out...or rather just "spin". I even put the stock hardware back in and it was the same. I did a fresh install of the OS on both the SSD and the old stock HDD, installed nothing extra whatsoever, and it was still the same, completely unusable. SO, I installed the newest version of Ubuntu on it and the thing was lighting fast! Faster than it ever was even when it was only like 2 years old. I could even run multiple Windows VMs without any noticeable slowdown.
One thing may be that I was not using it as often and those changes are done so incrementally that some people don't notice it as much/at all? Maybe the hardware is just junky, we did have a 4' stack of dead Macbook Airs, and a nearly 5' stack of dead MacBook Pros in the IT department of that company(why they let me keep mine). I'm running into the same issues on much newer Macbooks and MacMinis I was gifted a while back too. I cant say for sure why this is happening, if it is intentional, or what exactly is the trigger, but there is something going on, so for all those that say there is 100% nothing going on, you may wanna check you bias's. Cognitive dissonance is a b!#ch, I have been there before. Its amazing what your brain can do to save you from accepting something you really don't want to. Large expensive purchases have a way of triggering that sort of subconscious justification, been there too.
At this point I have clearly given up on avoiding digression and have moved into to borderline ranting, but having worked on computer hardware for nearly 30 years, I find the existence of "booby traps" inside their devices, doing things like geocoding parts to the location of the technicians they sell them to, so they can only be activated there (if GPS is accurate at the time that is), and making a mobo/CPU/RAM/SSD+ all one "assembly", pretty large red flags that they would be willing to do other shady stuff like the aforementioned possibilities. Think about it, their desired customer base are fiercely loyal, adverse to repairing their own hardware, well off financially, and willing to buy a new device every 1-3 years. How much push back from people like that do you think; slowing performance a little bit each update over a couple years to make the new device seem like a better upgrade, would get them? Sure people like myself who are not their desired customer may point it out, but anyone fitting the description of their preferred customer would almost never listen or just consider it tribalism/hyperbole if they did. Jimmy Kimble recently did a funny bit where they had Apple users "try the new iPhone" with their own data on it via a "special program that lets them transfer all their data to the new phone instantly"(fyi, if anyone ever says they can do that, don't give them your phone...no matter who they say they are,ok?). However all they did was distract them with questions while some fake technician behind them, wiped down their old phone really well and put it in a new case. EVERY single one of them raved about how much better it was compared to the last one. Including a guy that worked for Apple! It's part of that old, "why would it cost so much if it wasn't good?!" fallacy. MANY people will just assume it is and pay it, because $$$=GOOD, whether it is a product or a person, right? Just like how "we" tell people that hard work, honesty, and talent = "success" their whole lives, while we hold up people who achieved that kind of "success" as role models, and apply those virtues to them for doing so, even though that in most cases they reached that level of "success" via the absolute antithesis of those very virtues "we" claim to hold so dear. Ya'll buy Yeti coolers and Tesla cyber"truck"s too?! I would say it's a safe bet that is the case. Then again who would the coffee shop staff laugh at without those kind of people? They need those good laughs to get theough the day, so I guess it is providing some worthwile value. :-D