You have to accept that a server may fail to be accessible, whether it's yours or Amazon's. If this is an issue you add redundancy.
When you load lots of resources from God knows where in a way such that any single failure takes the page down, you are reducing the reliability that you could have had if the resources were all in the same place which you concentrate on keeping available.
If your site runs on AWS, it should run on AWS, not on AWS + Google Fonts + React CDN + Github + ...
But actually, there's nothing wrong with adding dependencies, granted that you correctly do your risk assessment. Are those developers assessing their risks and making an informed decision to add them?
I agree on that, I just don't see fonts as critical for your site, provided that you have a fallback. But I see how hosting the fonts is pretty easy to do and you avoid one point of failure for the user experience.
I'm really starting to doubt whether it's competitive to do your own thing anymore. And this seems to be getting worse.
Hard to compete with the combo of features & scaling that cloud provides. Attempting it pretty much guarantees you a gnarly trade-off somewhere (reliability, complexity etc).
When you load lots of resources from God knows where in a way such that any single failure takes the page down, you are reducing the reliability that you could have had if the resources were all in the same place which you concentrate on keeping available.