Yes it is insane. I am in same boat and have received mortgage applications, police details, applications for police jobs, massage receipts you name it. Many would be considered important leaks of customer data.
I have even had founder level emails that presumably are confidential sent to me because I share the name of someone operating in tech.
I respond or report when it's obviously some real person running a small group but for large monoliths there is very little to do except quickly reply to corporate email.
Really wish there was some kind of high level discussion about building something for this specific problem of non malicious wrong person same name errors.
Google could do it it's just not something that is monetizable at a scale they care about IMO and I have not been able to think of a way to make this work operating outside of email monoliths.
Would love to hear if anyone has ideas.
What Google has done, is add profile pictures for users, so if I'm emailing [email protected] I get her picture, but if I email [email protected], I see someone else's pfp which is enough to get me to realize I've spelled it wrong. I'm sure there's more they could be doing, but they're aware of the problem at least.
Commend your effort to actually contact the companies to let them know the error. I stopped doing that a long time ago when I stopped getting response or stopped getting any kind of meaningful reaction that I was actually trying to do something good by reporting it.