An update since my earlier post:
Amac (the store I bought my Macbook Pro M1 from), checked with other models in the store and it showed no difference. Apparently, at the moment it is supposed to look this way. They stated that it might get better after an update from Big Sur (but this post shows that this is an issue that was prevalent even before Big Sur). In any case, it is mind-boggling that I get a better camera picture on a similar model (base MBP) which is 5 years older. I really hope that Apple will resolve this issue one way or another. I've already sent in a complaint.
For those of you who cannot return their laptops because they really need a new one now (or were too late in returning it), I have found (to my mind) an acceptable solution: the app 'EpocCam'. It allows you to use your phone as a webcam and you can do this either over a cable or through Wi-Fi (which is not an unnecessary luxury considering we only have 2 ports now). While it is of course not ideal, it does give me a very clear picture while Zooming or Teaming (the irony is that it doesn't work with FaceTime...). The 'pro' version is 9€, which is considerable less expensive than a new separate webcam. As I saw that some people are resorting to using their older laptops for when they need a clearer webcam picture, this might be a more convenient solution.
Of course, it is insane that I have to resort to using a phone camera (in my case from the same brand) as my webcam rather than having an acceptable quality webcam built in already (and that in 2020..). But, alas, this seems to be the case and we have to make do. I would still suggest for everyone to send in a complaint regarding this issue and hopefully we will get a proper solution.