Different chips, different software, different purposes.

Actually, Apple recently pushed out updates for the TimeCapsule to address some firmware issues.

TimeCapsule runs NetBSD, and a fairly stout dual-core Cortex-A9 Broadcom chip along with a tuned Samba stack and an inhouse AppleFileProtocol stack and HFS+ on the disk - and all in-house development.

If you’re looking to replace a TimeCapsule - consider the QNAP/Synology NAS boxes - better support there.