If a site is updated and an old block is no longer used, or shouldn’t be used, but still exists on some pages, the block can’t just be removed from the field type as an assigned/allowable block, b/c then it’ll create errors if the editor loads an entry in which the block is used.

Add setting to the blocks to mark it as “Deprecated” - If marked as deprecated, the block will not appear in the add block menu list. Existing blocks will remain unaffected… users just can’t add a new one to the page. If deprecated, also hide the “Clone” button from that block.