If the only thing you're interested in is basic 802.1X/Radius (and you're a Microsoft shop), you could also look at Microsoft's Network Policy Server (NPS). We had it available as part of our Microsoft contracting, and it was a breeze to set up and configure. For HA, we just set up 2 NPS servers and mirrored policy configurations between them, then pointed our Meraki stuff at both of them.
ISE only for Radius is major overkill, IMO. Now, if you're looking to move into a more zero-trust security approach and have the budget/time to fully build out/utilize ISE's full suite of features, it's hands-down one of the better options. But just for radius? That's pulling a wagon with a semi.