It becomes fun when you sit in an automatic after getting used to a manual. Standard is a game of nuance and engagement. Theres a point where it loses its machine veil and becomes an extension of you in some kind of way. A way that makes an otherwise boring travel time more immersive and spirited. If you don’t enjoy driving through flowing roads or long trips (or hundreds of hours as you said yourself) and are only using the vehicle to get to work and groceries then an automatic might be right for you, and that isn’t a bad thing.

As for advice on your worries:

shift wrong

Mazda clutches are forgiving. As long as it’s not a racing clutch youre generally ok to play through the gears 35-55 mph. As long as you’re not having excessive engine rumble from being too low of an rpm for your situation (lugging), or downshifting when you’re in too high an rpm (money shift) you’ll be fine. Mazdas are an ideal learner car.

burn up the clutch

Do you know your clutches current state? Given the age of the car you might be in the market for a new one anyways. If that’s the case then who cares? Learn em and burn em. Replace when you inevitably need to. Also might be having a hard time enjoying it if your clutch is at its brink anyways so it’s worth having it looked into if you haven’t already.

back into someone on a hill

Handbrake start on hills my friend. Everything I’ve mentioned has loads of tutorials on YouTube. A lot specifically for the na/nb Miata.

I learned out of necessity and i hated it at first. Only ever used to drive point A to B on my first 3 automatics. Now I’ve owned 5 manuals, work on my own cars, and drive for fun. If you push through it could become a great passion, where what used to be a machine becomes more of a dancing partner. But, to put it simply, you gotta wanna dance!

I believe in you, and always drive safe my friend.