Affiliate links aren't a problem in themselves, but it's misleading and unethical to recommend a product without disclosing your financial incentives to the reader.
If you're in the US, this is a violation of the FTC Act.[0] Outside the US, Amazon still requires you to disclose that they're sponsoring your reviews. [1]
[0] https://www.ftc.gov/business-guidance/resources/ftcs-endorse...
[1] https://affiliate-program.amazon.com/help/node/topic/GHQNZAU...