"If" being the key word here. There are nuances to be considered. One DB might run really well on arm, the other not so much.
I'm saying it as huge fan of the arm servers. They are amazing and often save a lot of money essentially for free. (practically only a few characters change in terraform) In AWS with the hosted services (Opensearch, and such) there's usually no good reason to pay extra for x86 hardware especially since most of the intricacies are handled by AWS.
But there are workloads that just do not run on arm all that well and you would end up paying more for the HW to get to the performance levels you had with x86.
And that's beside all those little pain points mentioned above that you're "left to deal with" which isn't cheap either. (but that doesn't show up on the AWS bill, so management is happy to report cost savings)