Since people brought the "a few decade earlier was like that" response:
Old software on older hardware was «responsive» because library they used came with much less built-in capabilities (nice ui relayout, nice font rendering, internationalization, ui scaling), and also, less code means less memory, and rotating disk swap meant huge slow downs when hit, so being memory hungry was just not an option.
People that remember fast software was just people that could afford renewing their computer a year or so in the 20% top bracket prices, and don't realize that today mere inconvenient slugginess in 6-7 years computer was just impossible to imagine back then.
For the «let's imagine current day from that past», I would say we would be mostly in the same place, without AI, with much less abondance of custom software, and more investments in using and building properly designed software stack. Eg, we would have proper few UI libraries atop of web/dom and not the utter mess of today, and much more native apps.
Android might not have prevailed has it has, it relied a lot on cheap CPU improvements for its success.
Still safe language like rust would have emerged, but the roadblock in fixing compiler performance would have slowed down things a bit, but interest would have emerge even faster and stronger.