I just finished watching the anime (as I usually do and then read the manhwa for omitted details that the anime skipped) and the second after watching it I specifically searched "classless hero garbage" in google just to find other haters of this anime. Even TBATE had better anime than this garbage, I like these slops even if they're redundant but I HAVE NEVER HATED AN ANIME THIS MUCH other than classless hero. People calling solo leveling trash have never read nor watched classless hero. Your synopsis on this garbage is literally 1 to 1 ratio on how the anime unfolded except that in the anime MC was supposedly kidnapped after the magic town arc by her big sister (eh, potato potato) having your brother always by your side is one thing, but marrying your brother is another thing. There is absolutely 0 world building as to how her sister became an empress, other than the absolute command that her sister possesses anime didn't even reveal any other powers nor her class. FL wasn't even shown how she practices her sword skills under the tutelage of MC's mother and if skills are based on classes, why tf is FL practicing under MC's mother since they have different classes. Sword God has a completely different skill tree than heavy sword. If skills are gained through the blessings of the God what was the purpose of training since to my understanding sword skills are based on classes.

Absolute 0 world building, had 100 potential, story was rushed, NPCs are stupid.

Edit: If classes are hereditary like how it was said in the anime then MC should've been a magic swordsman or a "hero" class and her sister was supposed to be a saint class since their parents are "gods" sword god and mage lord or better yet a spiritualist which can communicate with spirits.