Blockchain is still like that. Today I am setting up a blockchain node. The chain is actually two chains that recursively depend on each other. The docs say to start one of them first and wait for it to fully sync. It prints a timeout error for every block, saying the other chain node software was unreachable, and is estimated to catch up to current block height in about 200 years, which can't be right. Maybe I need to run both nodes at once contrary to the explicit instructions in the docs which say not to do so.

I wouldn't be surprised if half of all blockchains were vulnerable to some kind of trivial double–spend attack because it's not possible that all the complexity has eyes on it.

Edit: you're supposed to download a 2GB JSON file containing the state as of the last migration.

The normal way to set up most blockchain nodes these days is to rsync someone else's node's working directory. Obviously this is worthless as far as a decentralised and trustless system goes.