Three/four years of (honest) work is usually worth to publish. The result might not be high impact (and thus end up in a lower tier journal, sadly) but knowing what didn't work is also a valid output.

If your soul can bounce back, finding ways your previous research might help, or combine with the breakthrough (or not !) can help. I've used many previous formal/analytic SOTA algorithms and methods for dataset tagging automation, or as feedback for RL, or to speed-up post-training.