The respective product companies will always claim that they offer the best and high-quality products. Well, my opinion is that if the product you're reviewing is something you would recommend to your mother (the general rule), you can use an affiliate link at the bottom. If you are clear about the negative and positive aspects of the product, you can surely write a good review. On the other hand, an email marketing SaaS is more likely to send a review email after the user has had their product for about a month.
The customer knows the real quality and the problems of the product, since many brands don't talk about many things that may be important to customers, since they are manufacturers, they cannot talk about the negative aspects of their products, but customers do, and this significantly helps other potential buyers to make the right decision, since they gain a good amount of knowledge about a specific product. Enthusiastic reports often make me wonder if you've ever really used this product, if you've tried everything the average user would try with it, if you've tried to “mess it up” and if the company that makes the product pays you for your opinion.