Why is it so important to have a 100% reusable spacecraft when you’ve lost more than a dozen of those “reusable” spacecraft while trying to make it work?

Seriously?

You don't understand why having a fully reusable rocket would be useful, even if it takes awhile to figure out?

Whether NASA should rely on it for the moon at this phase is an entirely separate matter, but humanity figuring out a fully reusable rocket is paramount to any proper space exploration. 12 launches to the moon isn't going to cut it, we've sent hundreds to the ISS alone.

Also, this is the 3rd version of Starship/Super Heavy.

The first version after a few tries was successfully going up and down and landing where they wanted.

The second version (essentially a new rocket) took a few extra tries, but was also mostly successful in that sense.

This 3rd version (also a essentially new rocket) has all the improvements they've learned from the prior two and should be the one they start doing real work with.

They even caught and relaunched one of the boosters on their first attempt, but now they're toying around with different descent patterns and burn patterns to eek out every extra % of performance that they can.

That's not the kind of thing you care about when it's disposable. Does it go up and deliver the payload? Yes? Done. Not, how much performance can we optimize out of this thing before we finalize it and start building thousands of them.

Edit: Just an example of performance gains - SpaceX successfully did hot staging numerous times with the booster being able to land exactly where they wanted. Then they were like, what if we can coax the booster (the size of a sky scraper building) to flip a certain way during hot staging, so we use less fuel overall getting it in the right position after separation? They've only tried this 2-3 times now, with it working at least once (can't remember if it was bad/good/bad or good/bad) but on the last v3 launch it had issues, which they will fix. Did they have to do this? No, what they did for multiple prior launches was working just fine, but because they are trying this out, they will be able to launch more payload per launch now.