Why are you so hung up on "gender"? Just replace it with "group" and you'll find the exact same situation in almost all languages.
In Swedish words are not gendered. But to specify the singular we use one of two groups. En or ett. It can be a word before what you want to specify. Or a suffix.
En banan, (a banana)
Banan-en, (the banana)
Or perhaps.
Ett körsbär, (a cherry)
Körsbär-et, (the cherry)
It's just one if two groups. Has nothing to do with gender. But if you really want to, we can pretend it's gendered because it doesn't matter. It's gonna be one or the other regardless.
Now tell me. How is this different from "gendered" languages? And as a bonus. There is NO rule regarding which to use when. You just have to know.
The question remains, why does there need to be two groups? Why can't everything just be "en" or "ett"? What does having both get you in Swedish that having only one does not?
Because äpplet means "the apple" while äpplen means "apples".
Because it's how the language works. Why do we have many, lots, large ammonts of words that all mean the same thing? Me myself and I don't really care because they are ways to express ourselves in different ways depending on what we want to convey, and how we choose to do so.
Gender often comes along with cases, which basically show you what role a noun is playing in a sentence. For example, is someone doing something, or is something being done to them. That lets you change the word order and keep the same meaning. You can emphasize different parts of the sentence, or just be more flexible with how you say things.
Here's an example from German:
Der Hund (subject) hat den Mann (object) gebissen. / The dog bit the man.
Den Mann (object) hat der Hund (subject) gebissen. / The dog bit the man. (Implied: That guy, and not someone else.)
In English, the meaning changes when you change the word order.
The dog bit the man.
The man bit the dog.
Languages do fine with genders and without. They're just different systems that happened to evolve over time. And languages can even change. English used to have 3 genders, but they disappeared hundreds of years ago. Instead of having like 12 different ways to say "the," we just have one, thanks to the Vikings and the Norman invaders.
I think the point is that it's annoying to memorize regardless of language and it's not like genders always make sense in other languages either. It is funnier with genders though.
It's like this in almost every language. You don't have to memorize it. You have to learn it. You will learn it by speaking the language.
I think it's mostly native English speakers that complain because everything is just "the" and the rule to a and an is very simple.
You can tell me a word in Swedish I've never heard before. But i will instinctively know if it's an "en" or "ett" word. How? I don't even know. One just feels more right than the other.
I'm used to it from German but having to learn which is which was still annoying. Luckily Latin has its genders built in to its nouns which makes it easier.
I think it's the fact that those groups are the gender groups that is causing the frustration. If it's arbitrary, why did it have to be the same system we use to classify organisms and personal identities?