Hello,
In the situation you describe (trying to recover a device), I presume the issue was that you had to remove or bypass Activation Lock ? That's a feature designed to make it harder for Apple devices to be stolen, by ensuring that you have to provide the password of the original Apple ID they were last activated with, even if you wipe them. So that way if someone were to grab your iPad right now and take it home and try to restore it via iTunes, they would still need your Apple ID and password to continue, thus preventing them from using the device (and thus making small-time opportunistic theft of Apple devices largely pointless).
Apple can bypass this feature, but - understandably, given that it is primarily a theft prevention service - would want absolute proof from you that you were the legal owner or the original purchaser of the iPad in question. That's the only situation in which I can think of where you would have to give out a "horrendous amount of personal info" to Apple: if you had to contact support, and they had to verify that you actually were who you say you were. In that situation Apple would need to check that the details you gave matched the billing address and the card they had on file for the Apple ID that had to be removed from the device, for example.
Other than the situation above (where you have to authenticate yourself to Apple support), I can't imagine why else Apple would need or want your personal information. I've been using an iPad for over ten years now, and other than very occasional contacts with Apple support over the years, have never had to tell Apple anything about myself, apart from my iTunes/App Store billing info.
I'd be very interested to hear more about what specifically you feel that either Apple devices or Apple as a company are collecting from you in terms of the aforementioned "horrendous amount of personal info", since aside from times when you need to prove you are who you say you are, I haven't myself experienced that phenomenon. You ask if there is a way to "stop apple collecting user data with launchd" - is there a particular service or application within macOS that you have special concerns about, privacy-wise ?
As to your last point - that the iMac you purchased in 2007 was not able to browse the Web as effectively in 2015, and that when its screen died you had no support - I don't think personally that sounds all that unreasonable. Virtually no hardware vendor is going to give you physical technical support eight years after you purchase a device. Third-party repair centres may still be able to carry out things like screen repairs, but Apple themselves would not carry out repairs on a device of that age, since it would long since have been out of warranty, and would also have reached the age where devices aren't eligible for out-of-warranty repair from Apple either.
Once a system is out of its warranty period, Apple have two levels of support: what they call "vintage", when the device is between 5 and 7 years old; and then what they call "obsolete", which is when it is more than 7 years old. Even obsolete devices can still get some very specific repairs on occasion - MacBooks may still be eligible for a battery swap, for example, if during their product lifecycle issues came to life with the battery in question.
Generally speaking, Apple have one of the best technical support policies in the industry. Very few vendors would give you any kind of support once you were seven years out from your initial purchase, but Apple still will help you with certain kinds of problems even at that point.
And lastly, in terms of software support, Apple devices actually tend to remain usable for quite a long time, especially when compared to other vendors. You mention your 2007 iMac was having problems with the Web by around 2015 or so; was it an iMac that was able to run the version of macOS that was available in 2015, or had it topped out at an earlier release ? If it was able to still run the current macOS, or a near-current version, and was being kept up-to-date, I would expect it to have still handled things fairly well, though of course any eight-year-old computer could reasonably be expected to struggle with things from time to time.
The Web is a very fast-moving environment where standards change all the time and at an ever-increasing pace, so unless a system can be kept up-to-date (or you can run a more recent third-party browser such as Firefox or Chrome), then you would find on a Mac that could not be updated that some Web sites would start to struggle, yes. So the key thing here would be the question of how up-to-date your macOS was in 2015 when you had these problems, and if third-party applications would still have been an option for you at that time.