I never argue with experience, but I will add that in solving problems we have a saying - one equation, one unknown (meaning you can't solve an equation if it has many variables).
My example had one unknown - megapixels today (and I would assert that pretty much any of the camera sensors from within the last year+ are of a day, give or take very little).
Your example has two variables - camera megapixels over the years.
Let's take a quick look at not too many years.
Early digital cameras were of one sensor type - CCD. There, each little pixel is captured by a device that holds charge, and it's charge level is read off and turning into a digital value after the image is "exposed." Trouble there - heat flow within the chip would change the charge levels in the pixels from the time of the exposure to the time of the read-off - and that would happen unevenly over the chip.
That all varied by CCD tech and chip manufacturing, which improved over time.
Then came the newer CMOS sensors - different way of skinning the same cat for converting light to digits and lots of extreme improvements in manufacturing that tech since introduced.
And what was the actual sensor size for those cameras you've bought over time? That has changed a lot over the years, from my understanding.
So - was the quality difference you saw a function of megapixels or it was it a function of simple tech improvement over time and they added megapixels because they could without harm? How can we be sure?
How about the image processing software built-in to those cameras? All the same jpeg standard? Maybe so. Did they all feature raw image outputs?
How about the accuracy of the ASIC processors? Maybe equivalent.
And how about the lens? We ought assume for fairness that you didn't buy any big changes there. Do we know? Lens are rated in lines of resolution. Did they use less capable lenses to keep costs down on the earlier cameras you owned? I won't go there, you can decide yourself if my assumption that they were equal is up to you, since you didn't say one way or the other.
I'll just stick with the sensor tech changes over time as too great for any of us to know at a glance - but generally, the physics will always favor the sensor quality over the raw MPs.
Hope that helps!
PS - You can click to enlarge my sample pics to their approximately HD resolution size.
PPS - Yes, once you hit the top in the other quality metrics, resolution then counts. I know a guy who photographs for the Smithsonian and National Geographic and his stuff is mind-blowing in detail - as are his image file sizes!
So - not saying that MP never matters - just saying it matters less than the other metrics before it.
Am saying I doubt it matters at all on a sensor this size if you have more MP compared to the noise specs.