Maybe so, but when characters that are widely considered "fair and viable" are asking for buffs to "compete"... that tells me that the top is too busted.
Alternatively, those people might also be huge pussies.
This is the only place in the FGC where the majority of people posting clearly believe that tiers are the end all, be all of skill.
To the point that anyone doing well with any character will translate into a double-digit page discussion about whether or not that character is "top tier", because that's obviously the only way anyone could be doing well.
People asking for buffs to a "fair and viable" character isn't an indication that the top tier is too strong. The statement is inherently contradictory. If there's a "fair and viable" character that is not top tier, then the top tier is not too strong. Just from a realistic, logical and grammatical standpoint. You can't have "fair and viable" characters that aren't top tier in a game where the top tier is too strong.
Quan Chi is generally considered top five by everyone with a copy of this game and a pulse. There is still a campaign for this character to receive a reliable wakeup attack and/or a six frame d1. People are bugging for buffs on a character whose one negative is that you must block occasionally.
The problem with a lot of matchups is that most of the roster breaks down to having one solid variation, one meh variation and one "LOL why did they even bother?" variation. Shit would look very different if every character actually had all three of their variants performing as advertised. You'd be able to approach a lot of matchups very differently.
The thing that makes the top tier appear busted is the ugly reality that sometimes matchup knowledge means jack fuckin' shit. At some point you will simply lose the coin toss and end up in the corner with 40% of your health getting torn out of your asshole on the way there. That's barely a balance issue, it's a far-reaching design flaw. You can't nerf that in a meaningful without totally trashing the character. Then D'Vorah's #1 and it's a fight between "nerf D'Vorah" and "no, execution requirements = balance hurdydurdyduhr."
I just don't see any avail in handing out more nerfs. I also don't buy the argument that "if everyone was buffed to top tier guidelines the game wouldn't be any fun", it's bullshit because I've seen it in practice through years and years of Guilty Gear (won't speak to Xrd, can't be bothered with that game yet). Every character in that game was a walking impotent rage inducing clusterfuck. Absolutely no one had anything worse than a 6-4 matchup even on the worst day. MK will never be able to touch that. This was accomplished with the relatively simple premise of "this character plays like __________, so we're going to give this character everything they need to play like ___________"
Characters slip through the cracks in every title, though. Vanilla Accent Core Johnny had no positive matchups but he was never dealing with anything worse than a 4-6, which is completely fucking winnable in all respects. The only real justification for nerfing the top tier at this point over buffing clearly useless character is "because easy."
If anyone thinks this game's top tier is more unmanageable and a bigger problem than the amount of characters that just outright serve no real purpose at a competitive level, you are a dead-eyed agenda pusher at best and a whiney, disingenuous little shit at worst. The idea that if you nerfed Kung Lao, Raiden, Quan, Tanya, D'Vorah et cetera and did nothing else, that your Takedas, Jacquis, Goros, Jasons and Mileena's would somehow be any better, you're drunk. The shitty characters will still be shitty if they're left to be shitty. They'll just have other shitty characters to keep them company on Shit Mountain.
It will always be a problem in NRS titles because they see nothing wrong with some characters having everything and other characters having nothing. The top tier are the top tier mostly because they're put together well. There are just clearly some characters and variations designed with no love. That's the bigger issue.
You can't pretend that relativity isn't a factor on tier lists. It doesn't matter how you nerf or buff, there will always be top and bottom. Which means there will always be complaints.
Personally I'm of the contention that this game is utterly unsalvageable. I doubt they're done patching so maybe we can get "The Patch That Saved MKX" somewhere down the line, but... my hopes are low.
