Been in a few orgs. I now think "no rewrites" is a good policy for all but a few orgs. Few orgs have the (1) business luxury (time and money) or, (2) the caliber of people and, (3) team motivation (few teams people even want to improve things) to pull off rewrites.

The best orgs do a rewrite usually in the face of sea changes to the technology stack (e.g., containers vs. VMs) or business use (number of users is now 10X of original etc). Bringing key infrastructure in-house is also a decent reason, but the benefit of building expertise in an existing ecosystem vs. full rewrite should be carefully weighed.

You probably have read spolsky's article. It's quite dated by now, but it's still more right than wrong. http://www.joelonsoftware.com/articles/fog0000000069.html