I've heard of some authors having these problems, on both Goodread and Amazon, and having trouble getting them rectified. I've never experienced it myself. As another commenter said, serious problems are likely confined to relatively few authors, which doesn't imply that it's not a problem. If it happens to you, it's a disaster.

It's easy to complain that platforms should do more to combat/contain problems like this, but the reality is (speaking as a software developer myself) it's not that easy. I guarantee you, nobody at either Amazon or GR is reading every single review posted. I couldn't find daily stats, but based on one chart that showed a relatively linear growth of 80 million reviews on GR over a 7-year period, one might speculate that over 30,000 reviews are posted there daily. If I had the mind-numbing job of doing nothing but reading reviews of books I know nothing about, and I managed to get through maybe 100 per day (which may or may not be doable depending on length), you'd need a staff of 3,000 of me to do nothing but check reviews. The company has less than 300 employees total.

So if you want to check reviews, you need to automate the process, and that is incredibly hard to do. It may be that the rise of generative AI can assist with this, but that technology is too new to complain about it not being effectively used for the purpose. Moreover, making major changes to software is time-consuming and expensive. Believe me. I project I recently worked on has the worst code base I've seen in 40+ years of programming. Everyone knows it needs to be rewritten. But where is the money going to come from? The current staff would have to be doubled to allow both re-development and support of the existing system until the new one is ready. And it will likely takes several years to complete the rewrite.

Can GR make it harder to get an account? Difficult to see how. They don't sell anything, so you can't be required to make a purchase. They can't verify your SSN, driver's license, or passport. They can restrict you to one account per email address, but you can easily create as many email accounts as you want.

More likely, the solution to such problems (on all sites) is an interesting technique that's been used on some community sites. In order to enter a review, they might require you to answer a few simple questions. Did you read the book? Where did you buy the book? How much did you pay for it? Was it a review copy? Post a text review (not just a rating). Requiring a few simple details has, on other sites, greatly reduced the number of spurious posts. It may also be possible to create an algorithm that computes a reliability factor based on your responses. The reliability factor can be displayed or even used to filter out low-reliability reviews in displays and when computing the average rating. This wouldn't be a panacea, because people could lie, but given how many people you say post, "I didn't read this..." it may help.