I suspect we may agree more than we might suspect (yo dawg I heard you like suspicions...) on how and where the government spends, I just don't think the focus on "taxpayer" funds is useful. If you're talking about lower level expenditure like council rates or some state levies I feel it's more applicable, not just because these entities aren't currency issuers, but because their services (could) operate closer to a user pays system.
I had a better post written out but lost it, but taxes are still important from an MMT (or whatever you want to call it perspective). They ensure that people use the government's currency because they need it to avoid being thrown in jail. Obviously they can influence the society/economy and even if they aren't technically required to "fund" government spending they balance the purchasing power of the private sector in relation to the public to limit inflation. A good example for this is war bonds: obviously no government would countenance losing a war due to a shortage of intrinsically worthless tokens that it can produce at will, but at the same time it cannot effectively mobilise the majority of society's resources if it's pumping money into a bidding war with the private sector, so war bonds and higher taxes are the order of the day (along with rationing).
After WWII when the US abandoned domestic convertibility into gold reserve banker Beardsley Ruml, who invented/popularised PAYG, advocated that since taxes weren't needed to fund the government any-more they should get rid of business taxes, because they were a drain/disincentive on private sector production and investment. Unfortunately economics is a messy discipline and the full implications of non-convertible (as in not pegged to a commodity or forex standard) fiat currency haven't fully percolated through. It's much easier to tell the simple "government = household" story and it doesn't help that such a belief supports certain ideologies. It's worth noting that the more Post-Keynesian monetary ideas (endogenous money, MMT, functional finance etc...) are seemingly much more prominent "behind the scenes" as it were than they are in mainstream economics: the BoE released a primer on endogenous money (which invalidates Say's Law and the money multiplier), Alan Greenspan famously declared that the US government has zero chance of default (he probably should have said unwilling default, because a Tea Party shutdown could force the issue), even the IMF has released papers suggesting governments with their own floating fiat currencies simply deficit spend without issuing debt. However, as I said, it's messy and that can lead to blind spots. During the GFC, Saul Eslake was in a story on the 7:30 report and said that "the one advantage that the US has that no other country does" was that even though it's government debt was large it was all denominated in US dollars which can only come from the US, so it could theoretically print money without the consequences that a different country might face (he didn't specify whether he meant for QE or fiscal policy).
Of course, that is an advantage Australia also has, but apparently one of Australia's most prominent economists was unaware of it.