Protip: I usually add a hidden input field to my forms. As it is hidden a normal user should not be able to fill it out, only a bot will. So if the hidden input isn't empty, I can disregard it as spam, it works wonders.
For heavier use cases (e.g. image processing), the user should be willing to spend some CPU power. It doesn't make sense to send an image to a server, put it in a queue, wait for an image processing worker to run it, and send back the result. It's simpler and more sensible to run that process client-side, if feasible. E.g. LLMs are too big for that, but many other tasks can.
Even the mobile oriented samey SAAS sites that have you scroll through 20 screens to read 5 lines sound better...
Edit: Btw, 100-500 ms on what? The latest Intel 500 W space heater? And tested only in Chrome because it's too expensive to notice that it's not very fast or responsive on other browsers?
Edit 2: Not to be misunderstood. If you're doing the computation for me, go ahead. If you're doing the computation because your framework has 100000% overhead, no thanks.
All browsers are approximately equally fast nowadays. I use Firefox, so no worries there.