You're describing individual personality shortfalls, not problems intrinsic to the role.

In the best case, they do split work, delegate, mentor, and lead meetings, but always end up doing the business critical or challenging pieces themselves (because why would I take the time to explain this when I could just do it...)

The best case scenario is seeing yourself as a facilitator first and foremost. A tech lead that succeeds at delegating, mentoring, and developing their peers does not need to do the business critical work ... peers should be able to do so, with some light oversight (design/code reviews). If some complex/business critical work is a couple months away, the lead should proactively work to disseminate their knowledge.

This parallels management - a bad manager micro-manages execution, a good manager builds mostly autonomous teams... a bad lead engineer micro-manages execution, a tech lead oversees a team of mostly autonomous engineers.

Sure, your team will move slower at the beginning. But think long-term, maximize the integral.