If an influencer tries a product given by a brand and genuinely loves it, and then shares their unfiltered experience online. Do you think people will be turned off? Absolutely not.
That is exactly what an influencer should do. But before sharing their opinion with followers, they should also communicate with the brand about their experience and confirm that the brand is comfortable with them sharing it.
This is the right way to stay credible to everyone (followers/brands) without feeling guilty.