You could certainly rework the voting system so that a wider mix of parties are elected to Congress (and every other level of government), but then what? At the end of the day, parties aren't important, policy is important, and enacting policy still requires some sort of majority. A majority, when you don't have a homogeneous population with largely similar views on everything, still requires some sort of coalition. And the coalitions you build affect the policies you can enact.
So how will changing the voting system, either to your current favorite or to some hypothetical, not-yet-invented voting system affect coalition building and the sort of policy that will be enacted?
Right now I don't even see coalitions being built by major political parties. I see political organization being transmogrified into factions and enemies.
I recognize that there are millions of dedicated activists and organizers who are building coalitions, building consensus, reworking political narratives.
For all that human effort to be channeled through the grimey distorting lens of left and right... Its wasteful at best.
I absolutely agree that issues are what's important. Unhooking the issues from the gridlock of corrupt political establishments would give elected officials the freedom to build consensus beyond the coersion of corrupted political parties.
Right now, the voting system is mechanically dividing the country against itself into two groups that don't really exist. Meanwhile, various corporate, media and political interests are capitalizing on this machinery in less than honorable ways.
This is enabled by the voting system on a foundational level. The other stuff, campaign finance law, media cultivation of ignorance, lobbying, etc... it's all very important, but it's all underpinned by the voting system itself.