Mind you, they immediately went and developed less harmful versions of warp drive; both Voyager and the Defiant are known to do better in this regard. There was less than a year between warp drive being found harmful and the Defiant getting pressed into service. Voyager launched a few months later.

Getting subspace-friendly warp drives into ships must've been an extremely high priority for them to retool at least two ship classes late during development.

(Also, it was mentioned a few times again, even if only barely. TNG mentioned it a couple times in the same season and VOY mentioned it once. Not much but something.)