It's not the Default vs. SSB thing, it's the fact that people were acting like Yuna's doesn't have any real use and pretending it was complete garbage when obviously if you DID get it, it'd be straight up better than Celes, but they chose to hand wave that. Heck, the argument when someone called them out wasn't even "well, Celes' SB is something you WILL have if you have the character, Yuna's there's a good chance you won't" nor was it a case of "suggesting people use Celes' SB and not Yuna's" because of that; it was people hand-waiving Yuna's as "useless" while holding Celes' to this "be all end all answer to all Ultimates!" level.
Basically, it wasn't "it's unimpressive for an SSB", it was just handwaived as straight up unimpressive period. Cloud's Blade Beam is Unimpressive for an SSB, for example, but as a general Soul Break, it's still stronger (elemental concerns aside) than any non-SSB and AoE, so you can't argue it's a BAD Soul Break. The context was in regards to banners and people were comparing it to Soul Breaks in general; if it was compared to other SSBs, that'd be a different story. If you go argue it's not worth pulling for, ok, fair, but to just go "nope, it's bad!" is completely different.
also, the Holy Weak thing is something that they never brought up, it was all "OMG EN-HOLY ON A PURE HOLY SKILLSET!" To put another way, Tidus clearly outdamages Cloud's BSB, pretty notably too and doesn't rely on RNG the way Cloud's does, but they hyped Cloud as having a superior BSB to Tidus, using "entry level damage lol" as the excuse even though Cecil has the exact same issue, and while there are more Holy weak enemies, they're still a minority and thus if Cloud's BSB > Tidus' on average enemy, the same argument applies to Cecil; you can argue to a lower extent, but it's still there.
What I'm saying is even if they have a good premise, they are awful at defending it since their reasons are bull****. Frankly, your "Holy weak enemy" thing is a better defense than what they were using, as they were assuming things like Basch's Shield. Curiously, what weapon gave Cecil his BSB? It's important because if it was Excalibur, that'd be a +20% boost right there that I don't think Tidus gets, which yeah, would be another point in it's favor...a point they conveniently didn't bring up as well. Yes, they put greater emphasis on Basch's Shield than the fact that there's multiple Excaliburs boosting Holy damage running around.
