So, how complex is software production? I’d say that there are seldom best practises but often good practices (in example DDD, clean code and the testing pyramid) on the technical side. And then a lot of exploration on the business side (iterative development).
So is a certificate of value? Maybe if you do Wordpress templates but not when you push the boundary of LLMs. And there’s a gray zone in between.
Credentials are insufficient for all of those. A credentialed plumber or electrician could flood or burn down your house and it might be hard to figure out the root-cause, so the credential slips. You still have to do due diligence to find competent people.
I'll admit that for certain things which are easy enough that you can write down procedures for them that a credential can be valuable, but there are a reasonably small number of those things in the world and even when you do write the procedures down you're usually significantly constraining the type of project that individuals in that field can undertake. That constraining is a very important trade-off to consider when thinking about whether a credential is helpful.