The fear with direct user research is that, unless you have a team and budget for getting enough of a sample, one-on-ones might not only be unhelpful but actively harmful if you implement something that solves that customers' problem but otherwise gets in the way for other customers.
As someone who’s run literally hundreds of A/B tests, many of them on the backs of UX research with users in the field, people have no idea what they want. The anecdata is a place to investigate, but never the end of the journey.
The major issue with A/B testing in the workplace is it causes confusion and slows people down when you change things. Which makes these tests really expensive even if they are seemingly easy to preform.