I know the OP said to keep it brief, but this will probably end up quite long, so bear with me here.
The main thing that comes to me when thinking about Scald is drawing the line between fishing for scald burns (or just going for scald in general) being something that is deemed detrimental to the game or something that is simply part of the game that we must all deal with. In my post, I'll be discussing ORAS solely, for now, and maybe I'll make a post about BW in the future if it gets discussion from others.
I'll start with and focus on ORAS OU because I think it's problematic in multiple ORAS tiers and I think it's worse there then it is in BW (which I may touch in a future post) given the nature of some of the metagames. The following "viable" pokemon use Scald often in ORAS OU: Keldeo, Manaphy, Slowbro, Politoed, Slowking, Suicune, Empoleon, Quagsire, Tentacruel, Gastrodon, and Seismitoad, but really only up until Empoleon or Quagsire are the pokemon common and noteworthy. I could go on and on about how the 30% burn rate restricts a lot of common counterplay and pivoting into these pokemon, but I think the best thing to do here is give examples and the best example by far is Specs Keldeo. Let's say Player 1 has a Specs Keldeo while Player 2 has a Keldeo counter, as every well constructed team has, like Latias, Mega Venusaur, or AV Tornadus-T (only three examples that are vulnerable to scald; things like bulky Starmie or Celebi would not be as troubled by Scald). Player 1 gets his Keldeo in safely, which isn't too hard to do generally, and instead of being walled by Latias, Mega Venusaur, or AV Tornadus-T if they come in on it or predicting the opponent and double switching out to something that gives you an advantageous position against one of these pokemon, it is now seen as a valid and even sometimes optimal play to click Scald and fish for that 30% burn chance despite not doing much damage (not even a 3hko on Latias or Venusaur while it's not a 2hko on Tornadus-T and Keldeo gets outsped) - the thing is that if you get this burn, then whatever check/counter they have is crippled for the rest of the game which: A) means they are limited in checking things - be it Keldeo itself or other teammates, B) forces them to recover much more than they otherwise would be assuming they have a recovery move - if not, then their survivability is essentially put on a timer, and C) potentially opens up a huge hole for Keldeo or a teammate of Keldeo to get by uncountered by the opponent if their main answer was crippled and subsequently weakened significantly or killed. Obviously, this whole process relies upon Scald burning, which is still only a 30% chance, but the effect that 30% chance has is significant and there is no denying that. Now the question essentially is: if Scald should be treated any differently than other moves with secondary effects & if the significant effect it has on counterplay enough to warrant a ban or not - I'll cover that now.
The primary difference between Scald and a move like Lava Plume is that Scald is a water type move inflicting a status typically inflicted by Fire types and their moves, so the switch-ins are prone to being vulnerable to the status it inflicts - essentially, any physical attack has been discouraged from switching into special attacking water types anymore dating back to generation five because of this and in itself, this is a hindrance on counterplay as exemplified above. Another thing is that Scald gets a lot more competitve use, due to the anticipated hinderance on counterplay and the fact that basically every water type gets it, in comparison to Lava Plume, which gets less distribution among fire types, is often not used in favor of alternatives (like Fire Blast), and doesn't have the same niche as a water type move inflicting a burn in general - overall, I'm echoing Bad Ass on this front that Scald and Lava Plume are not reasonably compared and equated with each other. Other status inflicting moves, like Body Slam, are also not as commonly seen as Scald, nor as convenient in general as Scald, but they're not fully comparable, so I'll just emphasize the fact that Scald is easily spammable in a competitive context and has a lot of upside when that 30% kicks in.
If scald is worth banning or not is really where I sit on the fence. On some waters, it is much worse than others. For example, something like Keldeo can easily spam it and then switch out with a 30% chance of permanently crippling a counter and having a greater chance of eventually breaking through while something like Manaphy appreciates Scald burning when it does, but is primarily used to set up Tail Glow and (attempt to) sweep the opposing team without fishing for burns over and over again and switching out upon frequently like a choiced Keldeo would. Other pokemon that are common and are seen fishing for burns without other intentions due to them being bulky or simply gaining a lot of convenient opportunities and having pokemon vulnerable to scald often switching in on them are Slowbro, Slowking, and Suicune (arguably as although its main focus is being a bulky cm sweeper, it is passive and bulky enough to fish for burns to speed up wearing down checks). It can thus be said that Scald is significant enough in the metagame to be controversial and given the crippling effect of Scald, I'd say that taking some tiering action on it would be justified, but I don't know if it is fully warranted or not - it really depends on how people gauge the 'brokennness' of the secondary effect it has. Personally, I'm leaning towards it being broken due to the limitations it imposes upon counterplay (which I discussed at length earlier), the fact that it encourages simply spamming a move for a secondary effect that is so crippling (leads right back into counterplay limitation) as opposed to making competitive double switches / predictions, and (this isn't much of a pro-ban point, but still worth noting) things can just use Surf, so it's not making many things less viable. Oh and also, I know I primarily focused on OU as that's my only area of expertise that's too relevant here (NU Scald doesn't appear to be controversial), but UU probably also is worth noting here due to the No Scald Ladder and all.