No, myTrailhead is a learning experience platform (LXP) that's designed around the needs of the learner, versus an LMS, which is designed for managers.
An LMS is top down and built for mandated learning, regulatory compliance, and record keeping, and typically has performance management capabilities. With myTrailhead, the learner is at the center with bite-size, gamified, customised content that's accessible to them when and where they want.
Most companies already have an LMS but it's no longer the only system used in corporate learning. myTrailhead is complementary to LMSs for companies that want to move to a more learner-centric model to drive a culture of learning.