I also like "simple". Lots and lots of very hard things are not at all complicated.

Hitting a homerun is straightforward, but it’s not easy.

I would argue the concept of hitting a homerun is straightforward, but the preparation, training and execution are not.

You’re arguing semantics.

The two words are synonymous in most casual conversation where you would be in danger of offending by saying something is easy or simple.

I think I was trying to agree with OP. Just giving an example that came to mind.

Conversely, setting up Jira is neither straightforward, easy or simple.