They ship you the tools their stores and authorized third parties seem to use to do a proper quality repair.

Yeah it’s heavy. But you don’t buy it, it’s lent to you (via a hold on your credit card).

I know people complain about this but should they send the battery in an envelope and say “good luck”?

Even if they design the phones to be more repairable (which I know many hope for), nothing can change the design of the phone you bought 2 years ago. And what Apple is doing is miles better than what they were doing before.