Some can, some can't. A degree is no guarantee that the person is able to perform at a high level, and the lack of a degree is no guarantee that they can't.
But none of that is relevant to my point, which is largely linguistic. If a person is doing a thing, then they are "a person who is doing the thing."
If a person is engineering, then they're an engineer by definition. That's not saying they're a good or bad engineer, just that's what they're doing.
There is a role for certifications, of course! But those certifications are intended to mark a lower boundary of ability, nothing more. Rather than overloading "engineer" to indicate that a person has a certification, I'd advocate calling them something like a "certified engineer". That would be correct and accurate, and wouldn't exclude a whole lot of great defacto engineers.
But none of that is relevant to my point, which is largely linguistic. If a person is doing a thing, then they are "a person who is doing the thing."
If a person is engineering, then they're an engineer by definition. That's not saying they're a good or bad engineer, just that's what they're doing.
There is a role for certifications, of course! But those certifications are intended to mark a lower boundary of ability, nothing more. Rather than overloading "engineer" to indicate that a person has a certification, I'd advocate calling them something like a "certified engineer". That would be correct and accurate, and wouldn't exclude a whole lot of great defacto engineers.