I still don't think FLUDD is better than Dr. Tornado as a lot of that stuff is situational / dependent on anti-airing poorly timed jumps and in some MU's you never get a good chance to use it to its full effect.
Dr. Tornado is always an important part of Doc's plan, FLUDD isn't on Mario. You can't tell me FLUDD is important in a MU against say, Greninja, or Sonic.. or my main Olimar. It's basically useless in those MU's outside of a quick panic button to get people off of you. They can each recover with EASE, and that's assuming you manage to even hit any of them with it. Olimar in particular can hard punish Mario for trying to edge-guard meteor him by clapping back with a DAir of his own to meteor Mario.. and with his Up-B / aerial mobility that's not hard to do.
I still don't see FLUDD as super valuable. It's a positional tool that sometimes cheeses people. Dr. Tornado has a ton of uses. Stage control implies you have control over an area of the stage, FLUDD doesn't give you that. Having someone far away from you OUTSIDE of disadvantage does not equate to having control. Especially if it's a character that benefits more out of being further away or has good edge game which Mario really doesn't.
The only character I play regularly that is threatened in the least by FLUDD is Ganon. I'm pretty familiar with the Mario MU, and I do not respect FLUDD the same way I respect Dr. Tornado when playing a Doc. Getting caught by the Tornado is always terrible, getting caught by FLUDD is sometimes bad and sometimes mildly annoying.
Greninja, and Sonic: Not too much. Sonic's Spindash ignores FLUDD for some reason, and Greninja's Low profile + Dash and Air Speed make it really awkward even hitting him with it. (Though it does help set up for good 2-frame attempts vs them at times)
But Olimar? Oh hell yea. It pushes him super hard if he's thrown Pikmin, Fsmash, or just tried foxtrot/dash dancing to bait an approach. (FLUDD even makes Pikmin toss miss usually)
IIRC Logic thinks it's one of Oli's worst MU's now.
FLUDD is actually pretty bad at actually edgeguarding unless it's directly FLUDDing a special. (And honestly the only consistent way Mario can deal with Ganon Nair)
At frame 21, it's fairly reactable. And actually pushes you UP if you DI it inward.
And Mario's edgeguarding itself is also pretty mediocre. FLUDD is almost entirely a neutral tool to help set up ledge traps and corner pressure. (And edgeguards against low tier recoveries)
And no, Tornado is NOT always a part of Doc's plan. He only has real confirms into it at mid-percents. Dthrow, Dair, and Pills don't confirm at all at higher percents. (But do into SJP which kills at those percents so it's fine)
FLUDD isn't always part of Mario's neutral, but there are matchups he simply can't win consistently without it. Like any anti energy character, disjoints, heavy zoners, etc.
I honestly don't fault anyone for not quite understanding the benefits of it. It took me a long time in smash 4 to realize it. The best example I can find is actually in smash 4 of me vs Remzi:
https://www.youtube.com/watch?v=3wkGWd5_1Co
First game I just approached and got punished hard. Next 2 I just FLUDD camped due to all the jumping around. (I almost beat Marss like this too, but double SD'd at 10~% trying to STP but didn't b-reverse so I SD'd :T)
FLUDD is even better in this game. And Mario's long-distance game as a whole, really.
I will say you, though you may be right he could be better off with Tornado simply because uair would confirm into it, essentially a straight upgrade to fair or cape. And it'd give him a WAY better recovery, and edgeguarding tool. But his neutral absolutely would not be better, just his advantage/disadvantage.