Q: Why won't certain Google sites/pages work properly in Safari?

For some time now, Google's Blogger site has not worked properly in Safari. The blog creation/edit page loads, but the cursor does not function in the text box, making it impossible to edit.

Now, today, I was unable to log in to the Google Play Books Partners site, which wouldn't recognize my log in, sending back to the login page.

Not surprisingly, both sites/pages work perfectly in Chrome.

Is it a basic incompatibility (which would suck)? Or is there a Safari setting or extension that could be causing the problem?

(The only Safari extensions I have installed are 1Password, Pinterest's Pin It button and Adblock. I disabled Adblock; it made no difference. I've had the Pinterest and 1Password extensions for years, long before this was an issue, and have them on Chrome as well, so I don't see them being the issue.)

Any ideas would be welcome!