No, I don't think it's only about "more complex websites", "more taxing multimedia" and so on - it's more likely also macOS and Windows bloat and questionable software quality getting in the way. I recently installed Ubuntu Linux with the LXQt performance-oriented desktop environment on a 10-year-old Intel i7 2600 workstation back from 2011 (16 GB RAM, an Intel HD Graphics 2000 built-in GPU, an Intel SSD with specs archaic by today's standards) and the system is extremely fast and responsive at everything including web browsing, multimedia playback, IDE-based development (e.g., CodeBlocks), app launching, etc. Website content and multimedia rendering alone is not enough to saturate even a 10-year-old CPU/GPU.
Yeah, right. If website content and multimedia rendering alone is, demonstrably, not enough to saturate even a 10-year-old CPU/GPU under Linux, then no, it is not possible for "a new Mac" to be even faster at same content and multimedia rendering. It does not make any difference, productivity-wise, whether you render website content and multimedia at 60 fps, or 120 fps, or 240 fps - the eye perceives the same thing. Effectively, whatever you pay for "a new Mac" over the cost of a 10-year old, generic PC workstation is being used exclusively to accelerate macOS.
For me at least, I’d say the prior versions of windows were pretty zippy whereas now I don’t even know what’s going on behind the scenes and why it takes so long to perform basic tasks, even with 16 gb ram.
One of the things I think is all the performance improvements.
By that I mean performance improvements that sounds like they should be faster, but don't scale as well as simply brute forcing.
The other is "security". My work Mac has 3 different VPN/Network Proxies and 2 malware checkers. I would assume that each one is caching network details, as I have to go in an disable/enable them all once or twice a day to restore network performance.
It's like the whole multiple anti-virus conflicts on Windows again like no one ever learnt.
My MacBook runs at 120hz super reliably. Everything feels basically instant. It kind of turns me off using my gaming desktop since despite having far more power, the experience is not as slick and responsive.
Beyond that, what actual stuff are you talking about?