The basic infrastructure of Hive can support vastly more users, it would just be that resource credits and accounts might run out during an onslaught of signups - but that can be remedied if necessary.
I have already posted numerous articles on the topic of downvoting and censorship that address your points, but I appreciate that you may not have seen them. This has been going on for some time.
https://peakd.com/hive-181335/@theycallmedan/saqwofmi
I also spent two weeks building a front end just to track Downvotes, which did not exist previously: