If a person speaks a very complicated language as his native tongue, would this make it easier to learn other languages?

In most languages, there are certain rules that are obeyed most of the time. In many Romance languages, verbs usually end with one of a few different verb endings, which are conjugated by uniform rules. English is more uniform when it comes to the gender of nouns. Almost all English nouns are neuter, except for when the object is physically a male or female. In the Romance languages, there can even be two nouns that are spelt the same but have different genders and mean completely different things.

In the above examples, a native English speaker might find it easier to know exactly how to conjugate a verb, while a speaker of French might find it very easy to learn the gender of English nouns.

Let us pretend that there is a made-up language Complexinese. Complexinese is a very irregular language, meaning that there are very few rules that are uniform throughout the language. It would have many noun genders, a lot of irregular verbs, complex pronunciation rules, and any other features that might make it more unpredictable.

To a native speaker of Complexinese, most other languages would seem to be simpler and more predictable. Does this mean that other languages are actually easier for this person to learn than for other people to learn? Or is it just an illusion, that while it seems easier, it doesn’t actually speed up the time taken to learn the language?