there's this "cartel" of big mines that effectively verify all the money. Those full nodes just keep a record of it.
first of all why do you use the term "cartel" here?
secondly miners do NOT verify anything. they are only performing a tedious task of computing hashes. it is the nodes that verify transactions.
You can't send or receive bitcoin unless one of these big mines agrees that you did by putting it in a block.
if a miner rejects a transaction, another one picks it up. if a pool rejects a transaction then miners leave that pool for another one. if things get bad and a large number of miners turn malicious the nodes would create a fork and turn their millions of dollars investment into bricks by changing the mining algorithm.
in other words miners are kept in line by the nodes.
I was quoting someone else who stated that mining is "cartelized" - was simply sticking with the wording they used.
It's the miner's who are completing blocks and therefore stamping transactions as part of the "permanent record" so to speak.
Like you said, right now if a pool proves to be malicious (or even gets too powerful, as we've seen in the past) then the smaller miners can choose to jump ship to another pool. As mining continues to have higher and higher requirements due to the ever-rising difficulty and the proliferation of these mega-mines, there are fewer and fewer who can make that decision to change in any meaningful way.