Does working in a research group with poor funding means poor future prospects post graduation?
This is hard to judge without knowing a lot more about why there is a lack of funding. It might be a local problem, in which case you might be fine. But if the funders generally don't value this field or even this line of inquiry within it then you could wind up in trouble. In that case, you need to be prepared to be flexible in the lines of inquiry that you commit to.
There is an especially sad case at the moment. The woman  Katalin Karikó who did the fundamental research (mRNA) that led to the development of two of the current COVID-19 vaccines, was, if I understand it correctly, denied promotion to full professor at the University of Pennsylvania since she was unable to attract sufficient funding for her research. Finding no future there, she left for industry. Moreover, her research shows promise for attacking cancer generally, which is a pretty big deal.
This was extremely short sighted on the part of Penn, of course, but at top universities funding can be a critical issue. And, of course, it is also proof that even the funders of research don't understand the nature of research and the impossibility of a guaranteed outcome. There can be a certain risk aversion that is counterproductive, though funds are limited.

I suspect that Penn is kicking itself at the moment as it doesn't share in the recent mRNA patents. Perhaps that is a suitable comeuppance.