You can appreciate the longevity and continued support of an iPhone without having an Apple Watch. You can appreciate a MacBook for its OS (pre Catalina anyway) and build quality (I'm still running a 2014 model -- though I have read about recent models' issues) without having an iPhone to pair it with. To be fair, you cannot appreciate an Apple Watch without an iPhone at all since it won't do anything, and I'm no the fence about AirPods and how well they do outside the Apple world.
My point is, once you're in the ecosystem, you notice a lot of little things that may make your life easier. Are they great? Yeah absolutely. Are they what sells the product? In my opinion, not at all. Unless it happens to pinpoint your exact use case (I need to lock and unlock my MacBook 30 times a day and I'm tired of having to enter a password, I want my Apple Watch to unlock it), it's the product itself that will most likely convince you. The way they neatly play together at times is just the cherry on top, like when you notice your computer and phone now share a clipboard. That's awesome, but not a single selling point for anyone.
Now, I will be the first one to say: iTunes sucks. So, if you do buy an iPhone, it makes sense IMO to shed out the extra 99ct a month for iCloud storage.
I didn't want my comment to sound like I'm saying Apple does it best. I just wanted to drive the point home that I don't think it's mainly the ecosystem that makes Apple devices fun to use.
As a side note, I wasn't talking hardware that lasts 5 years. We all know most devices on the market now can pull that off, bar one battery-replacement. I was rather talking continued software updates, where iOS is certainly in the lead.
Edit: just re-read your comment and you were talking Apple computers specifically. Oh well :)
I feel like that only furthers my original point though. I didn't want to argue that Apple does it best, only that you can enjoy their devices without being fully bought into the ecosystem.