Wealth only indirectly influences GDP. If you had 1billion dollars’ worth of Sony stock and don't buy, sell, or receive dividends then the impact on US GDP of you owning that stock vs. someone in Japan is zero.
When you break it down short term GDP growth is dominated by the size of the working population and changes in the value of your currency. Over the long term you need to consider technology and infrastructure improvements but wealthy society’s both expect more from the government and can afford to have their government provide more so that's not really an issue. Thus linking government spending to GDP is fairly healthy activity.
PS: I would happily to drastically cut a lot of government spending, but I also realize doing so quickly would be vary damaging to our economy. I think a flat 25% federal tax including social security that starts at 70 and universal healthcare and excluding any and all tax breaks would be close to optimal, but good luck getting that passed.
Growing with population or inflation makes sense, at least for costs which scale with population. Growing with gdp is nonsensical.