When you talk about it being a cash grab, do you mean that there's something particularly bad about Leviathan, or are all DLCs cash grabs?
And how did Leviathan make the lore worse?
Well, I take all dlcs which are in some way multilating a core plot as cash grab, all dlcs made for ME3 were cash grab in certain way, but least shady was Omega due that it was planned to be a part of ME2 not the ME3, but at least it´s not breaking into the core narrative, even plot fits more intho second installment and if you ask where did I get it - yes it was mentioned by someone I guess Walters, that they had a plan for this DLC since the release of ME2, but they never used it till the ME3.
I do find acceptable dlcs which are for free at day 1(despite I did preorder of CE, otherwise Shale was great one) or ones like Overlord (Wardens keep, etc...), but I really don´t find acceptable DLCs which are comming with some core narrative themes, which should be already in game. In the other words, From Ashes and Leviathan are both the same as you cut out of ME1 Sovereign and Vigil and put them into the DLC with name - Understand to the core narrative...
And how do Leviathan lore worse, well you have no idea if Leviathan is not lying, than also if he knew about all the stuff, why he simply haven´t mentioned the Catalyst´s position, weakspot, hardrive or bluebox - just whatever - killswitch, instead of answering the question you recieved more or less vague answers which were hardly convincing, not to mention le´Crucible.