The underlying technologies very rarely change and offer very stable APIs. Apache has been around nearly 30 years. NGinX nearly 20. Both offered major advantages over existing solutions, but also interfaced with the rest of your codebase using a standard mechanism (CGI) so you could easily migrate to or from them.

A single vendors solution will not (at least very much should not) become a standard underlying technology, so this isn't moving to the next underlying technology. You're just tying yourself in to one vendor.

If it gets standardized across vendors or open sourced then it becomes a different story, but until then its a massive gamble to assume it will and the standard chosen will derive from your current vendors solution. Then what happens when the vendor decides to double prices and kill the free tier (also known as being acquired by Oracle)? deprecate it? Goes bust? etc.