“Taoism”, the religion, has, as I am given to understand, many of the normal trappings of religion, including formal dresses for priests, and, IIRC, quite a lot of alchemy.

This is probably not the “Taoism” which you read about in western pop-culture paperbacks or hippie-age TV.

Perhaps they have priests with costumes, and I am not aware of any alchemy, but are these "shortcomings" in any sort of fundamental, materially important way?

It's 'internal alchemy' [0]

https://en.wikipedia.org/wiki/Neidan

Ah, thanks for that. These seem fairly harmless to me but I'm not so knowledgeable, what do you think?

I think they're things best practiced with a guide, and not something to go attempt yourself. Whether there's any actual effect from it or not, who knows. But it's always better safe than sorry.

I mean, alchemy is not a really an advantage for a religion to include these days. Most religions have dropped their medical claims long ago.

It's worth noting that modern Daoist alchemy is internal alchemy [0]

[0] https://en.wikipedia.org/wiki/Neidan

Sure, but I am more interested in this idea of whether alchemy is a fundamental and substantial part of Taoism, and then also the question of whatever negatives may come with that (if it is actually true), is Taoism in the aggregate net beneficial to humanity, or not. I'm curious if you have any thoughts on the matter.

The major religions and also secular ideologies each have their strengths, otherwise they wouldn't have millions of followers.