Human societies face a collective action problem. If we want to do or make stuff, like food, or art, or medicine, or Tik-tok videos then this going to require a) a decision to do or make that particular stuff and b) the organisation of c) the relevant resources and labour sufficient for the doing or making.
Capitalism is by and large our answer to point b) and c). Capitalists (i.e. investors) provide resources - mostly in the shape of money, but if you own land, or a factory, these are perfectly good resources in their own right, for example. Some of the money resource is used to hire both workers to do the labour and managers to organise it.
The prior question a) - how do we decide what to do or make - is currently answered by the operation of free markets, mostly. Strictly, this isn’t completely integral to capitalism. You can have - as the Allies did in WWII - command economies where decisions on what to make and do are in the hands of government, and private investors and labour are assigned accordingly. But free markets - i.e. societies in which what is made and done is largely an emergent property of (constrained) individual preferences - tend to march alongside capitalism quite happily.
If we’re not going to use capitalism and/or free markets to decide what we’re going to make and do and how we’re going to make and do it, then we need some other system. We’ve variously tried communism, feudalism, despotism, theocracy, Big Chief, Wise One, plus others. Some of these have been pretty successful by their own lights - you don’t build the Pyramids or the Great Wall or the Tsar Bomba without being pretty good at directing and organising labour and resources. None of them, post industrial revolution, have been as successful as free market capitalism over the long-term.
But - and not to get too Marxist - these relations of production are very much bound up with productive forces. I.e. how we organise our society to do and make stuff depends a great deal on the means by which stuff can be made and done. A society which produces things based on human muscle power alone is different from one which produces things based on human and animal power, which is yet different from one which has steam engines, oil, electricity, etc. A society where information is controlled by a small elite has different economic arrangements from one where everyone is literate, or one where everyone is literate and has a smartphone. Ditto for other technological progress in e.g. financial sophistication or the ability to transport people and stuff.
So what if anything replaces capitalism will in many ways depend on how we do and make stuff in the future. Will abundant energy, automation, and increasingly sophisticated AI mean that we as humans basically no longer have to worry about organising resources and labour? It’s a nice idea, but maybe a bit too utopian. Will accelerating climate change and the resulting societal breakdown push away from the freedoms necessary for free-market capitalism and return us to some form of neo-feudalism? Let’s hope not, eh?
But generally, I think your vision of what replaces capitalism, or how capitalism evolves, will be dependent on your view about how social change - often driven by technological change - will alter the options for economic organisation.