The issue si that way more people live in big cities than this ein rural areas. I general humans tend to give more importance to their local issues, and having a proportional vote makes the issues of rural areas go unheard, since the big cities will refer for most of the money to be destined to their issues.
At a glance it makes sense, for most of the money to be deestined to the majority of people but rural areas also need repairs, upgrades, and projects to renovate them, since they are the ones that produce and sustain the big cities (in theory, I know that with globalization it gets a bit muddled). Districts exist to make the voice of those that sustain big cities louder, to make it fairer for them.
However, the travesty that is the US has perverted this notion to create completely manipulated regions for their benefit. I would propose for something like “vote power” to exist, so that each vote gets multiplied with some number that is computed from the population of the region that vote was casted or other significant reasons, and then to add all of those votes.
For example, people living and voting in a small town would have double or triple voting power than those living in a big city. The citi will still get in total way more power, but it would help to balance that difference a bit while not letting those in power to manipulate the districts in their favour. This is vulnerable to those in power to manipulate the vote multipliers, but that is way easier to regulate than imbalanced and weird regions.