Like, English is a famously difficult language, and Spanish is supposed to be easier. But babies learn English or any language instinctually.
So do babies learn faster if the native language is easier, or do they acquire language at a constant rate depending on their brain development or whatever?
English is easy to get started but insanely hard to master. There are tons of irregular verbs, orthography is all over the place, plurals have more than a few pitfalls, etc.
It is the most schizophrenic language. Super easy to be understood even getting most of a sentence wrong, but can change meaning entirely with just a comma. Has at least two different root languages and as many as five depending on how you define root. Has words from almost every spoken language on the planet and has so many spelling exceptions you can have high level competitions just trying to spell different words.
And all that is just the tip of the iceberg.