Security updates are always a good thing, though the new Anniversary Update yielded a lot of problems for a lot of people (I had some BSODs due to Avast! myself, but no idea who's fault that is Microsoft or the anti-virus software). Also a lot of the privacy settings get returned to default without it asking you (on the Anniversary update alone). The last is actually more like what a Service Pack used to be than a simple update.
For me, aside from the before mentioned update I have had no problems with Windows Update, and I was in the same boat as you are with the previous versions of Windows (XP up to 8.1), never using Updates.
So: is there a chance MS fucks up and you'll get a less stable system after updates? Yes. Is it therefore better in this day and age to connect to the internet with an outdated Windows... Hmmm, just really (you probably aren't) don't use Edge or IE then.
I'm fine with the updates, trust MS or not, think about what Google already knows of you, or Apple if you have any of their products. On my first smartphone I had ALL location services off at all times, but on the net I could still find my everyday movements over a period of a couple months, with Google sometimes guessing (correctly) where I lived and what my place of work was, and I checked if my location services options were off every week.
So, in conclusion, is any big tech coorporation to be trusted? No. Can you have total privacy? Yes, live like a hermit and don't use anything connected to the internet ever. Is it worth it? No, probably not. I'd say just install the updates