problems with citation-based metrics
The biggest problem with this kind of metrics is that incentivizes scientific work in fields that are ripe for receiving citations[ @bhattacharya2020 Stagnation and Scientific Incentives ]. Now that there is a multitude of scientists working on PCR, a paper using this technique will fall into a community that will find it easy to cite and build upon. However, very early papers on PCR may have not received as many citations, just because there was no field using it.
The question the authors in [ @bhattacharya2020 Stagnation and Scientific Incentives ]ask is who collects the benefits in these situations: people who took risks early on or the people who built upon and got the citations. They two examples they use is the development of PCR and of CRISPR, which were multi-decade endeavors on which a lot of preliminary work was needed for them to become successful.