If you can insert the word "like" and "as" into what people assume is a metaphor, isn't it really a simile? [duplicate]

In this article:

https://blog.prepscholar.com/simile-vs-metaphor

The author uses a popular Katy Perry lyric "baby you're a firework" as an example of a metaphor.

Katy Perry could just have easily said "baby you're like a firework" but it wouldn't have sounded as good.

So isn't this kind of like a "fake metaphor"? It is a very simile-like comparison but people call it a metaphor just because it doesn't use the words "like" or "as".

To provide a different example, if I were to say that I longed for connection to my spouse but due to past trauma I found myself hiding behind a wall, that seems a much stronger example of a metaphor.

In order to express the same sentiment as a simile, I would have to say something like:

I longed for connection to my spouse, but due to past trauma I had distanced myself by creating a set of behaviours that were like a wall.

So you could still say the same thing as a simile but it would be totally stupid.

Therefore shouldn't we be teaching people that if you can insert the word like or as into the metaphor without making any substantial changes to the syntax, then it's not really a metaphor?

The real difference is the degree of similarity and signifies the degree of intensity.

Katy is a firework

states equality. Its degree of similarity is higher than

Katy is like a firework

A metaphor is simply a more intense simile.