I've rarely seen alert() used in the past few years outside of as a means of harassing users on malware sites (have you ever accidentally clicked on a malicious ad on a mobile phone and struggled to escape the site due to alert() spam blocking interaction? It's terrifying as an end-user). This seems like a more than reasonable decision given an adequate phase-out period.
And what happens when Google makes an unreasonable decision about what should be a part of the web standards and what should not? Who even has the capability of making them reverse course at this point?