Sometimes I shoot film with a 30 y/o old camera. (Old camera but new medium ... Okay not quite apples to apples.)
For me, it is all about capturing the exceptional image. Better hardware, typically, makes that capture easier and increases consistency. For what I shoot and how I shoot ... and for most of us, after a certain baseline of IQ, better hardware does very little if anything in contributing to the success value of an image.
Presently, my main cameras are Fuji's @ 16mp. (Yes, there are many factors other than MP's that affect IQ ... But I'm just addressing MP's for now just to keep it simple. But life and photography are never simple.) Generally, I find 16mp sufficient for my needs as I don't print larger than 16x13. I don't shoot much landscape or architecture, mainly people doing stuff, from Streets to Sports to Theatre. For me, at 16mp, image impact (composition/timing/lighting) has a significantly greater impact on success than image quality.
But I think 4mp is a bit below that said baseline.