I'd love to see some practical tests done. Like just layout a microcontroller PCB and use different decoupling caps and see how that affects things like max working SPI frequency or something.
I made a test PCB with capacitor footprints repeated at various intervals, with measurement ports for controlled experiments. You can really see the performance difference between two and four layer PCBs, for example: https://jmw.name/projects/exploring-pdns/
I don't suppose you ever did the measurement with big-V decoupling, and with and without the big electrolytic? That would have been really interesting.
Like many engineering problems, filter design rarely has a universal solution. Many MLCC exhibit resonant piezoelectric and or electrostrictive effects. Thus offer marginal noise floor performance in VHF/UHF LNA, and sometimes introduce more problems than they solve.
The main reason MLCC are so popular... is the price. =3
It's also probably dependent on who made them, and the engineering of the materials they used. After all even if every cap meets the spec but there are several paths to get to the spec.
