Define "bad". I'm on a 2019 MB Pro with an i9 with 32G of ram. I pretty much never have browser performance issues that bother me. I have Chrome open with 2 windows and a total of 39 tabs, plus some other apps that people always like to bitch about resource-wise (Slack, VSCode). Granted I'm not a designer so I don't have what would be some of the most resource-hungry apps like Figma, but if there is one group of people who I've always seen spend a shitload on their desktops/laptops it's designers.
I think Mighty was always a weird project that pretty much only solved a problem for people that would never be willing to pay for it.