My question is: does this tax money get spent on the poor, or is making the rich richer?

Both. Today's rich are wealthier than the rich of the past, but today's poor are also wealthier than the poor of the past.

It's also the case that quality of life differences have shrunk between the two groups, not because life has worsened for the rich, but because it's improved for the poor. Bill Gates' car, music, TV shows, phone, pants, meals, etc. aren't that much better than the average person's, today.

In the UK, it seems that it's mostly spent letting the boomers live long and relatively luxurious retirements that younger generations can only dream of.