You almost get the feeling that something is broken when you load Gmail at this point. The Gmail interface is... fine I suppose, but I'd much prefer a native client. Sadly the best you can hope for these days is Apple Mail, and that's also just "fine".
Ever tried Mailmate?
In the end I just setup email in the Mac email client.
This was in the latest Firefox, and I know chrome is supposed to perform better for gmail, but writing an email on a 3 year old laptop shouldn’t be a big issue, but here we are.
You can press Command+Shift+R to force reload and it works fine afterwards.
Also, running GMail in Firefox (on MBP) makes Firefox consume 100% of a single CPU core very often. But if I open developer tools to track down the source of the problem, it stops consuming 100%.
Well, at least they stop me from checking e-mail too often. I used to check e-mail like 5-6 times per hour before. Now I do it 2-3 times per day and I feel like it increased my productivity on stuff that actually matters. So, it isn't all that bad ;)
According to https://support.google.com/mail/answer/15049?hl=en, the following link should set it to basic html mode (I haven't tested it)
I've used the basic html mode before when the normal (js heavy) one was a bit slow, and it ended up being much faster even if every action requires a whole new page request/render.
Today I'm struggling with 8 GiB of RAM and 2 cores. Admittedly I have many tabs open, but that is to be expected. Web site creators might believe that the world revolves around their web site, but really it does not, and so they must share my machine.
Weaker systems are of course unusable. Suppose the hardware is a 32-bit PowerPC Mac with one core and 512 MiB of RAM, and there are a bunch of tabs open to similarly taxing web sites or worse. I've mostly had to retire a system like this, which makes me really annoyed because it is quiet due to being fanless.
Note that the "weaker system" described above is not really weak. Long ago, I used the old gmail just fine with far less. There was a time when 32 MiB of RAM was enough to open several browser windows (we didn't have tabs) and run them. JIT didn't even exist yet, but the web ran fine.
It's the usual problem I think: software developers are rewarded with high-end developer workstations to keep them happy and productive, and then they test the software all by itself on this high-end hardware and everything looks good. Nobody is testing on older low-end hardware with lots of other things running in the background.
Also, Guest & Incognito seem to be intrinsically faster for some reason even compared to an entirely fresh profile, so you may want to compare against an empty profile instead.
I do work for Google as a web engineer, but not on Gmail and have no insider insight on gmail speed.
I have gigabit internet and I can assure you it's not a bandwidth problem.
Gmail will completely freeze for ~10-15 seconds while performing a search.