The only PC where I saw Gmail being fast was a Ryzen 9 3900x build, I suspect that if Google devs were given shittier PCs they'd build faster products that would appeal more to the average user.
I have a Google-issued corporate workstation with 64 GB of RAM and 12 cores. Gmail is really really slow. Like so slow that I if I have to refresh it I'll go get coffee. But I'm on Firefox, and so "I Am Not The User" and all that.