Three different reasons to leave, and a different answer for each.
Vault is still the most capable tool in the category. Teams look elsewhere for three distinct reasons, and mixing them up leads to the wrong replacement: the BUSL licence is unacceptable, the operational burden is too heavy, or IBM ownership has made the roadmap a question mark.
The licence answer. Forked from the last MPL release, Linux Foundation governance, familiar API.
The operations answer. The same class of capability with no cluster to run or upgrade.
The simplicity answer. If Vault was always more than you needed, this is the honest downsize.
The scope answer. If you only ever used Vault as a key store, the cloud service is cheaper and simpler.
Before migrating, audit what you actually use. Teams often discover they run a Vault cluster for two secret engines — which changes the decision from a migration project into a weekend.
Tell us which clouds you run in, whether the requirement is keys or secrets or both, and whether a regulator is involved. You get a shortlist and the reasoning behind it. Your details are not passed to vendors.