He makes an interesting point that we are coding programs that run more slowly now than they did 10 years ago. Javascript has only gotten faster over the last decade, computer have faster CPUs and more RAM. The problem is the frameworks and the programs have gotten slower.
What did we gain exactly? Reddit is better at displaying videos and images now. But it's slower despite faster hardware.
I hate the state of affairs. That said my guess is what we „gained“ is tons of telemetry, tracking and the likes, engineers not needing to think about performance to get a feature out, which absolutely lowers the bar to entry, high level abstractions and ux and visual bells and whistles of varying importance and quality (infinite scrolling, streaming updates, image blend modes, blur effects, scroll timeline animations etc). People creating Pokémon had to think about every bit in their texture atlas and carefully manage the hardware memory manually. Web devs now try not to forget to clean up event listeners in a useEffect that triggers on mouse move to generate data for an interaction heatmap for the marketing department while 25mb of 3rd party scripts make sure every data broker and their mother is well informed about your digital whereabouts.