True, wendy couldn't stand when facing bluenote. BUT she also wasn't using dragon force against him and before she could do anything natsu showed up. Wendy without dragon force has shown an impressive level, at least 1 year back we have every reason to think she was at least a match for jubia (as shelia was). Add in further training from that point and the multiplier from dragon force... Also, I didn't say wendy would outright win, I'd say she'd be able to do something. And yes, I do remember natsu being scared shitless. But he also didn't use dragon force (and I am not 100% sure if he used or not lightning flame but that is besides the point). Dragon force gives natsu enough of a boost to be able to keep up with mard geer, whose actual stats were quite high. It's not that absurd that natsu would have been able to hold his ground at least for a bit against gildarts with such a boost had he used it at the time.For starters, Wendy couldn't stand under Bluenote's Gravity. How can she possibly best Gildarts?
Half the guild? That's a pretty outrageous exaggeration. There's a case for Natsu and Laxus, but how exactly are the others above Gildarts (as of the silent chapter)? You do recall Gildarts was still strong enough to toy around with Natsu and send him flying and then scare Natsu shitless after showing a serious attack. And then Gildarts has crash and disassembly which works on both magic and people. That's seriously underestimating Gildarts tbh.
Well, but natsu clearly isn't the only one that has powerup up to such a ridiculous extent. If anything the manga requires at least that to continue. We have seen grey sparring more or less evenly with natsu (though I will grant that it was just a spar) and he did pretty well in holding back ajir. Erza did pretty well against ajir in general, she merely getting him to use his full power is more than enough indication that she is easily above above gildarts as we know him. Lucy is the sole reason they even defeated jacob. And she was able to copy marin's magic which specifically implies her magic is above him even though he was a guy capable of negating space time magic literally through all of magnolia. Gajeel being anywhere near natsu would as well imply he is well stronger than gildarts and even if there is a difference he probably has access to dragon force as well which at this point would easily put him above the gildarts we know. Laxus is straight up a match for a springan... Saying half the guild would beat gildarts is hyperbole but at least the relevant fighters in the guild seem to have had dramatic increases in power.