Earlier quoted context omitted.
Probably because it is 10 year old older hardware but thoroughly tested. Using Chrome/JS/CSS on the latest Ryzen might be neat but when you need to transport 300 passengers daily around there is other sort of concerns then taking up 3 folks to the ISS every 6 months.
That is no excuse. It was possible to create almost instantly responsive UIs more than 20 years ago.
This is an airplane after all, not a consumer-grade gadget.