Sadly, any Goodreads competitor will need to miraculously gain the network effect; everyone you know is on Goodreads, so it'll just be you and whoever you can convince to move to a new platform.
As for the downsides for Goodreads, this blatant lack of moderation is troublesome. I also dislike that Kindle / Amazon are the only visible links to purchase books by default. Amazon already dominates the ebook/audiobook market, so I also simply dislike Goodreads due to their acquisition by Amazon.
Once upon a time I bought something online for about $10 from what was a legitimate business with an address in San Francisco. About 14 months later they claimed I subscribed to some service and started making huge charges to my card ($150/week). Getting them to stop and getting my money back was an enormously stressful and difficult process.
That's why I have a knee-jerk reaction - not a cold, logical reaction - to online purchases from companies I haven't used before, and I'm not the only person like that.
I've had incorrect subscription charges on one of my cards, and while it was minorly annoying (a search on the card website, fill out a form, repeat one more time the second month it happened) I can't imagine a scenario where it would be "enormously stressful and difficult".
Your card issuer is required to respond when you report fraudulent charges, and if they don't you need a new bank.