It's one thing to argue over whether basic user facing software like an image compressor or a text editor should have telemetry, but a web browser is one of the least controversial scenarios for telemetry I can imagine. It is constantly sending and receiving data on your behalf with hundreds or thousands of servers spread across the internet as a user agent. Your usage patterns - i.e. is it crashing, is the feature you're trying to use failing to work for some reason, is it rendering at a good framerate, is it running out of memory, are you having trouble finding the information you're looking for - are going to be incredibly complex and specific to you.
Significant bugs can affect only 1% or 0.1% of a browser's userbase but at Chrome scale or even Firefox scale that's like a million people. If you don't have telemetry it is REALLY hard to hear from those people about their problems and understand them. There simply are not alternative solutions that work half as well as opt-in (or opt-out) telemetry. People who say web browsers don't need telemetry are simply ignorant of what it's like to ship one and try to keep it working in the face of a constantly shifting environment - broken drivers, broken VPNs, malicious websites, malicious extensions, broken hardware, and users who are confused or tired or simply just bad at using software. No one is speaking on their behalf, you have to dig their suffering out of the data by looking at crash reports and performance metrics.
Shipping a web browser used by a million (or a billion) users means that you have a responsibility to do a good job. If your browser is not well engineered and reliable and responsive to users' needs that can result in data breaches or third-party server outages when your browser misbehaves or incorrectly channels user intent.
I'm personally a fan of making usage telemetry opt-in instead of opt-out, but browsers are a case where I don't opt out because I know how important the data is for browser vendors to make informed decisions.
This is of course different from sending your browsing history to Google, Microsoft, or any other company. I encourage people not to opt in to that stuff and not to sync their history/bookmarks/etc to those companies.