The claim might just need correction to say, "Many philosophers say that simplicity is a good thing but the requirement is not enforced very well by philosophy journals" or something like that. I think I believe you, but do you have an example citation anyway? (SEP entries or other ungated papers are in general good; I'm looking for an example of an idea being criticized due to lack of metaphysical parsimony.) In particular, can we find e.g. anyone criticizing modal logic because possibility shouldn't be basic because metaphysical parsimony?