At the very least, that the vast majority of nodes are running the default software (i.e., core) - most likely completely uncritically in most cases, strikes me as an inherently systemic danger. Even if I were to run a node under the philosophy of blindly facilitating any and all transactions, i would seriously consider running knots with a customized configuration to do so; even if only for the sake of diversifying influence over the network software as a whole.