MadBliss

const [rankLogo, setRankLogo] = useState(mmrLogo);
...
const checkMMR = () => {
  if(input >= 800) {
    setRankLogo(mmrLogo2);
  }
  ...
}

const elements = document.querySelector('#list').children;
// или
const elements = document.querySelectorAll('#list li');

const getVal = el => +el.textContent.split(' - ').pop();
// или
const getVal = el => parseInt(el.innerText.replace(/.*\D/, ''));
// или
const getVal = el => el.innerHTML.match(/\d+$/) | 0;

const sum = Array.prototype.reduce.call(
  elements,
  (acc, n) => acc + getVal(n),
  0
);

// или

let sum = 0;
for (const n of elements) {
  sum += getVal(n);
}

// или

let sum = 0;
for (let i = 0; i < elements.length; i++) {
  sum = sum + getVal(elements.item(i));
}

// или

const sum = (function sum(i, n = elements[i]) {
  return n ? getVal(n) + sum(i + 1) : 0;
})(0);

// или

const sum = eval(Array.from(elements, getVal).join('+')) ?? 0;

const elts = document.querySelectorAll("ul#list li");
let sum = 0;

elts.forEach(elt => {
	sum += Number(elt.innerHTML.split('-')[1]);
});