At one time, web browsers competed in the number of third-party add-ons, sometimes known as extensions, they supported. The extension system allowed the browser to remain slim, at least compared to the behemoth that Internet Explorer was while leaving the door open for functionality that browser developers had not envisioned or even intended. Wasn't either. Of course, this requires that the software have hooks that extensions can connect to in order to implement those features, including sometimes being able to modify what users see on a web page or on a user's computer. Touching files is also included.
Although Google can be praised for taking up the cause of banishing harmful cookies and trackers from Chrome and the Web at large, there have been doubts about the company's ulterior motives. In particular, its proposed compromise to replace those cookies is put into question because they seem to benefit Google only, particularly its ad platform business. And, of course, Chrome is being used as the vehicle to push that on the Web.
Perhaps the biggest problem with Chrome's large market share, and the reason why users should turn to potentially better browsers, is that it gives Google too much clout in the direction that the Web is going. If Google decides that Chrome will block sites that use this or that technology or require that sites implement a new feature, most websites will have to adjust to cater to Google's demands. At times, that works in the Web's favor, like pushing HTTPS to become the standard. Other times, however, it seems that Google is the only one to really benefit in the end, like when it "encouraged" websites to use AMP (Accelerated Mobile Pages).