You seem genuinely interested in this topic. One I spent a considerable time researching last year and left me disillusioned. A study that may help is from professors Adam Dyne and John Holbein: Noisy Retrospection: The Effect of Party Control on Policy Outcomes. It’s quite a read but demonstrates:
Our results suggest that voters may struggle to truly hold government coalitions accountable, as objective performance metrics appear to be largely out of the immediate control of political coalitions.
Simply put, in large elections with millions of people, our votes count very little.
We should still vote. It matters for local elections, but when it gets to the state level and higher, the impact of our votes have little to no effect.