Highlight the text and you're good to go.
This is an extremely complicated question but there are a huge number of factors. Firstly: Starcraft 2 (and the expansions) is easily the best single player RTS of all time, nothing else comes close. So they did that part well.
Secondly: Brood War was balanced by accident and SC2 was attempted to be balanced by force; the latter is always worse and leads to "meta" gameplay which is horrible of course, a modern Blizzard concept that destroyed any of the fun in playing multiplayer games well by forcing you to have a 50% win rate; which is only fun if you're terrible. Note this concept is rapidly dying in modern game design so we won't have to deal with it for much longer, much like Bioware's shitty restrictive and repetitive RPG design finally gave way to the Witcher 3's expansive design.
Thirdly: DotA killed Mapmaking and thus killed the replayability and the heart and soul of the community. Now by the time SC2 had come out Indie games would have killed mapmaking for obvious reasons (it takes months upon months to make a good BW map), so technically it doesn't matter that DoTA killed mapmaking. BUT DoTA did kill mapmaking and thus all true brood war fans must inherently hate DotA for by and large murdering the entirety of the RTS genre; else they're not really RTS fans. That said I eventually got over it and occasionally have fun with mobas (a word that sounds like dota)
It should be noted that I played with the creator of DotA/Aeon of Strife and every other good UMS map in Brood War at one point or another (Panzer-Kavalier, Melkor (WC), Ar-Adunakhor, Fenix'01, Theromangeneral etc.); he seemed like an innocent enough fellow (as did the TROP 1.2 creator Isildur (WC) which greatly simplified the excellent LotR genre and made it a lot worse for several years (eventually the good maps that Melkor (WC) came back around; though ironically I met Isildur playing SC2). So I don't place the blame on the map creators; it is the fault of the community for abandoning other map genres, many of which could easily be the biggest game in the world right now since nearly every mobile game genre is just a Starcraft UMS map remade.
As to the Indie Vs DoTA killed Mapmaking genesis question its impossible to solve like any great philosophical conundrum. If DoTA doesn't exist then obviously the entirety of twitch/streaming/esports and a whole lot of other shit is completely different. But I still think we can guarantee that SC2's mapmaking scene never would have took off because you could just make an indie game instead. Now granted there's only like 5 or so actually good indie games (FTL/Into the Breach/Spelunky/Isaac/insert favorite indie game here) and the rest are all just somewhat worse version of SNES games; but the fact that a lot of them are limited in scope etc. is very similar to how Brood War maps were made. But since in BW you're working with a limited toolset as opposed to the limits of your imagination in modern toolsets it was much easier to find like a linear path to a great map with the limited tools available instead of having countless Steam Greenlight games that aren't even close to half baked. I must've played at least 1500 maps I enjoyed to one degree or another and I'm still waiting on my 10th or so indie game that I actually enjoy as opposed to seeing where it could be better in numerous fields.
For me personally the decline of Starcraft led to my embracing console games instead of only playing a very limited number of PC games forever; so it was probably a net benefit aside from the loss of countless friends (I did reconnect, briefly, with a handful when remastered came out at least, the nostalgia vibes and the beep boops at match start in ASL/KSL streams are enough to stave off depression)
