> Spanish has much more complexity
All this tells me is that you haven’t learned either Spanish or English as a second language learner. Spanish is incredibly consistent. Unlike English, once you learn the alphabet, you can read everything in Spanish correctly.
> It's spoken all over the world.
That has zero to do with how hard or easy it is to learn. There is absolutely no correlation. It is spoken all over the world because of British colonialism, American cultural exports, and it being the lingua franca. Not because anyone actually would choose to learn it if they had any other choice.
Linguists categorize languages according to how hard they are for people to learn. Spanish is a category 1 language (the easiest to learn). English is a category 4-5 language (out of 5).
“Is English the hardest language to learn?
Given what we’ve already noted, you might be wondering if English is deserving of an equivalent ranking as one of the hardest languages to learn. Well, that too is a very subjective opinion. After all, people who are already fluent in languages that are related to English—particularly the Germanic and Romance language families—probably won’t find English to be that bad. However, English has a lot going on that could make it very frustrating to learn, even for a person fluent in one of these languages. Here are some of the commonly cited reasons that English is often considered to be a very hard language to learn:
English is an unusual mix of Germanic and Romance languages. Many English words are taken directly from Latin and Greek without changing their form or meaning at all.
The rules of grammar, pronunciation, and spelling in English are largely inconsistent and sometimes make no sense at all. For example, the past tense of ask is asked, but the past tense of take is took. Additionally, there are tons of exceptions to these rules that need to be memorized. For example, the beloved “I before E except after C” goes right out the window when we run into a word like weird.
English is full of homophones that are pronounced identically but have different spellings and meanings, such as the words way and weigh.
Often, English synonyms can’t be used interchangeably. For example, you often mean two different things when you say that someone is clever or when you say that someone is sly.
The order of adjectives is often based on what “sounds right” rather than a formal set of rules. Often, native English speakers know the “correct” order of adjectives without even actually learning it.
All of the above issues cause problems even for native English speakers when trying to use proper grammar and spelling. Needless to say, a new learner is likely to struggle quite a bit when trying to wrap their head around the ridiculous rules—or lack thereof—of English. We may not be able to say for certain that English is the hardest language to learn, but we think it definitely makes a serious claim for the title.”
https://www.dictionary.com/e/hardestlanguage/