The key issue isn't Lucas or Allen. The key issue is Lucas/Allen as a type. Those who gloat over the probable omission of Lucas were even more scathing about Allen before Lucas came in earlier in the season. They don't appreciate the usefulness of attending to the midfield basics consistently and before any other qualities come to be considered for the midfield. They'd be glad to be rid of Lucas, and when the time comes they'll be glad to be rid of Allen too, in order to get in a more "dynamic" CM. And by dynamic I mean someone who doesn't do so much of the basic work, as the basic work is often denigrated (until a period when the lack of such results in the midfield not working), and every quality but the midfield essentials is highlighted as a plus (and the essentials are assumed to be part of any package, when this is pointed out).
You're quite fond of this line of argument, but I think you'll find almost everyone in here appreciates what Lucas and Allen do. I personally like to gloat about our form without Lucas because there's a Cult of Lucas that likes to attribute all our improvement to him, but he's certainly played well this year when he's gotten in the game and restored balance to us. I'd also, however, be perfectly happy to be rid of Lucas in the summer, as he's slowing down physically and gets injured a lot, though only if we get another midfielder who can do the Allen/Lucas things well, perhaps with a bit more progressive ability and mobility than Lucas.
I suppose you might have a point when we dream about Pjanic--and I must admit I think a Pjanic-Henderson midfield would do pretty well, if perhaps not to the point of being worth Pjanic's transfer fee--but almost no one is trying to argue we don't need midfielders who do the simple things.
If those of us who like the more "dynamic" midfielders like to mock anything, it's those who have seemed desperate to sign the new Momo Sissoko. I definitely want a Joe Allen in my side, but I can't abide these glorified center backs playing midfield.