Very rarely do I give advice on RMT's. But when I do, I try to give it on how to improve the pokemon that the poster has listed. I'm pretty sure that the poster is aware that there might be pokemon that do the same job better (like Swampert over Quagsire), but I try to understand things from their perspective. Sometimes it's not just about winning. It's also about having style and your own sense of individuality, and trying to bring out the best in a certain pokemon. In a way, it's a test of a persons skills as to how well they can adapt. Winning a match is only half of the satisfaction. The other half comes from knowing that your own individuality and creativity helped along the way. If I just wanted to win, I could easily throw a Salamence, Metagross, Swampert, Gengar, Weavile, and Blissey on my team. Give them items and movesets depending on the theme of the team, and I'm good to go. In less then a minute, I've created a powerful team with a nice balance of offense, defense, and resistances.
But where would the fun be? Where would the style be? Now if I came up with this team with creativity, then there would be no problem. But I've come up with this team for winning purposes. I don't just want to win, I also want to have fun while doing it, otherwise what was the point in doing it at all?
Now don't get me wrong. I agree with Phuquoph. The majority of the time, people post RMT's to know how good of a chance they have of winning with "said team" depending on what said "tier" the team is most likely to face, cause we all want to win, right? But people want to win without feeling like that have to use "said pokemon" in order to do it. People want to feel like they can win with just about anything...
Now in the past generations, things were pretty much set in stone for the most part. Raticate couldn't beat Mewtwo no matter how much it tried. But now with some new items and moves, Raticate could use Focus Sash to survive the Psychic, Endeavor, and then finish with Quick Attack.
My point is that a lot of pokemon have been given new potential and power that they didn't have previously, and some of it hasn't been reached to the fullest extent. So for some raters (not you Phuquoph), since they don't know the full potential of a certain pokemon, their best advice is to substitute something else.
For example, if I made a RMT with Raichu on the team, I already know that at least 25% of the raters would say to switch Raichu with Electivire or Jolteon, cause they "hit harder" or "have more speed". But what these posters don't know is that while Raichu may not hit as hard or move as fast, it has other options. It can kill Swampert, Gyarados, Rhyperior, and Salamence all in the same moveset. And the sets that I listed in Raichu's thread effectively take care of Focus Sash users. Oh yeah, Raichu can also double his special attack, can Electivire or Jolteon do that?
IMO, RMT's should first look at unlocking the full potential of a pokemon. If a change in moveset does that, then go with that option. If the pokemon just doesn't work with the theme of the team, then, and only then, should a suggestion for substition be made. And raters should only suggest substituting a pokemon if they know the full potential of said pokemon first.