BBC writes about the loss of Moody's triple-A rating by the UK. And halfway down the article you'll find this:

This means it will take longer for the government to reduce the budget deficit - the amount it has to borrow as it is spending more than it gets in through tax revenue.
That is because when an economy is not growing, companies and individuals are paying less tax, and it has to spend more on welfare payments such as unemployment benefit

And this is why modern capitalism, of the sort witnessed by anyone living in the early decades of the 21st century, is a failing system; perpetual growth simply cannot be at this scale for any economy (other things being equal of course) and in this context cherry-picking criteria for ranking people, organisations and countries -- let alone forming the basic operational frameworks by which society functions -- is flawed (at best) and dangerous (at worst).

The main problem here is that moving away from this model goes against centuries (and trillions of dollars' worth) of interests and investment. But we need to move away from this model, we need to 'reform' (not abolish) capitalism simply because in its current form it has lost any sense it made before.