I agree with you, in spirit, but I think the true issue lies elsewhere.
Rich people can spend money to influence elections, yes, but how can they do it? through political donations, super-pacs and bribes. Bribes are already illegal. political donations and super-pacs can give politicians the juice they need to get their messaging out, but getting the message across isn't enough to win an election. The people need to vote. Billionaires can spend as much money as they want to support candidates, but a billionaire still only has one vote to cast.
My point is, billionaires can pay for all the political campaigns in the world, but the electorate gets the final say. It's up to us to A) run for office and B) vote for the best candidate (but tell that to the 64% turnout in the 2024 presidential election)
Elections are important, but they're just one part of the political system. A lot of machinations and politics occurs outside the scope of elections or even of the public eye.
Money doesn't just buy ads. It influences the decision of who is a candidate in the first place. It buys operational range. It pays salaries for the right friend of X, the right family member of Y, etc. It buys other bribes, etc.
Consider watching this: https://www.youtube.com/watch?v=qnOmUWd-OII