I’m going to ignore the security angle and post my big fear. Chrome has dominance similar to IE at the height of its popularity. Whatever you think of their decisions, Apple is the only thing stopping a 90%+ Chrome web. (Note: not why they’re doing it, just a side effect) People keep arguing Apple is being anti-competitive. But no one seems to recon with the possible consequences of what they’re asking for. And I fea…
First, IE was bundled onto virtually every computer at the time and Microsoft went out of their way to stop you from replacing it (eg system actions would use IE).
Second, Microsoft's anticompetitive IE behaviour was aimed at protecting its Window monopoly. Microsoft was worried that the Web would become a device-indepndent platform and that would obviate the need for Windows at all.
Third, is Chrome actually bundled to any large degree? There's enterprise bundling but how significant is it? There are Chromebooks but I feel like they're not a huge factor. I guess there's Android. Chrome's desktop share seems to be 68% [1]. That's impressive for an action people have to take to change the default.
Fourth, Google doesn't have the same motivations as Microsoft (in regards to protecting another platform). There are other much more real issues (eg favoring their other properties like Youtube) but crippling Chrome doesn't seem to be something that aligns with any of their interests. It seems way more likely that Youtube (etc) will work better in Chrome. While that's bad for other browsers, it doesn't have the same negative effects as what Microsoft tried.
Fifth, the core of Chrome (ie Webkit but also V8) is both open source and the core of other browsers (notably Safari and Edge) so it's less likely Web developers will end up in a situation where they effectively have to implement something twice, once for Chrome and once for the rest. That was pretty much the situation with IE.
Will it be a big deal in the future? Maybe. I don't really see this being a big problem anytime soon however.