Let me ask you something. What is needed to make a tier list and see how good a character is. How does one determine this in your eyes?
Okay.
What is needed?
It needs information. What is information? Well when it comes down to it, especially at the level of a tier list (which is an "opinion") the information we use is opinionated as well. I hope that the information that voters use is based on sound knowledge and application of their own or others, which takes into consideration the potential bias involved (*cough*pitmains*cough*). Things like frame data is a low level (in terms of building blocks) knowledge that coupled with move set design create options; through the understanding of options we make notions of match ups, and at high level thought about all this comes "viability". I can't expect everyone to understand each level (and nor can I with every character in such depth) but for the information needed to create a tier list, participants must at least have a level of knowledge of all characters in the sample they're looking at (whether that be people who are only voting on high tiers because their opinions aren't definite elsewhere). The tier list creation is by standard done by voting, and in order to make the most accurate tier list for the time I hope those who vote only do so in things they are informed about.
Viability is really abstract, and a lot of people in the BBR who are active players can be told about the things that make up the lower levels, but it won't entirely convince them until it is SEEN in an acceptable tournament environment -> theory can only go so far. I can personally see a lot of things about Peach that are great and amazing, and many people in the BBR would be aware of those things too (god bless you DP), but they would still be uncertain of how that amasses in total. A character may have an "amazing option", but what if that option is rarely applicable or potentially avoidable?
As I said the tier list is done through voting, and fortunate or not (I'd say more not) that is a prerequisite to any system used in it's creation. To make an accurate tier list, there needs to be a system to create it that will produce something "accurate" after taking into consideration the opinions of the voters.
Once upon a time, perhaps maybe around the time that I decided to take up the last tier list project, I proposed that voting would be mostly stripped up until "small samples" individual ranks. We would use the character ranking list (to determine how often/common a character would occur) and attach that with the BBR's thoughts and opinions of match ups to create a "tier list". In the same way that we can see amazing things about Peach but not be sure of the validity, taking away the highest level from the BBR as individuals to try and strengthen the levels below it had some contentions.
As an engineer I'm well aware to make a working system you start from the top and work downwards (in terms of articulation/thought/planning); but the lower levels are what equates to the higher ones indefinitely. We would only strengthen our publications by doing so. But for the time being I/whoever else runs it has to make do - and honestly I am/was pretty proud of how this tier list eventuated.
To continue on, not every individual in the BBR will be happy with what "theory" creates when making a tier list. And I doubt we'll ever be able to do so. "Viability" is required to be an opinion, not based on theory in ye ol BBR (as well as every where else, honestly)