If someone has “more” then yes of course someone needs to have “less”, merely by definition.
The question is really whether those with less are living below the poverty line or living comfortably. I guess it’s a question of semantics whether “capitalism” requires people to be living below the poverty line but I don’t think it does. It’s just shitty regulations which allow wealth to become as concentrated as it has.
Socialism in principle sounds great, but most times it’s been implemented it’s suffered from the same problem as capitalism - the people with power are greedy and use their power to manipulate and oppress the populace.