SC2 is a beautiful game, as a spectator sport and as a competitive activity. I've put about thousands of hours into the game, achieving Masters in 1v1 ranked 8x. I've thought long and hard about what Blizzard could have done to make the game more popular from the get go. Some of my thoughts:

1) The multiplayer should have been F2P from the beginning, and the campaign should have been a buyable add-on. Valve was already doing this on top of the in-game paid cosmetics, and Blizzard could have easily copied their business model for SC2. The game was ripe for those kind of additions.

2) The original UI was far too heavily focused on 1v1 ranked. The reason games like SC:BW and WC3 had such long-term and widespread appeal was because of how easy the casual modes (custom games, big team games) were to access.

3) Blizzard, in an attempt to prevent another Kespa power grab situation, created very restrictive rules for non-Blizzard SC2 tournaments that effectively prevented a large number of independent tournaments from being run. This goes in stark contrast to a game like DotA 2 where Valve put little regulation on independent tournaments which allowed the scene to thrive organically.

4) The official tournament system for professional play was terribly implemented from the get-go. Region locking was a very short sighted idea used to give a boost to non-Korean players, but it was wholly irrelevant as Korean players won every tournament anyways and effectively made the early rounds of Blizzard tournaments much more boring and predictable because you would have mediocre foreign players getting smashed by the Korean players. If Blizzard did this again, they should have simply let the "best" players in, regardless of their region. This is why the GSL was always the more exciting tournament - the player base, from top to bottom, was always far more talented than the WCS.

5) Implementing MMR decay was a terrible idea - it caused a huge number of competitive players to abandon the game for games like League of Legends and DotA, where they could take a legitimate break from the game and come back and still face similarly talented players. It was good Blizzard went back on this, but they damaged the game's competitive playerbase with this move.

6) For too long, Blizzard was far too afraid to make sweeping changes to their game in the same vein as DotA or League. As a competitive player, I don't mind this much, but to keep players coming back, doing major game altering updates is a guaranteed way to keep your playerbase coming back. Very recently, i.e. with the most previous expansion (Legacy of the Void), Blizzard has been actually doing some serious and interesting changes to the game that I believe will keep it fresh and fun while the core game stays intact.

Making the game F2P is great news, and certainly the book is not closed on SC2. I hope Blizzard does not give up on the game now that it's F2P and instead focuses on growing the game organically again. SC2 tournaments should have the same hype levels as a major boxing match - everyone who follows esports should at least tangentially be aware of it happening. The game has the potential to be that kind of spectator sport, it's just up to Blizzard to keep working on it at this point and keep player interest up as best they can.

I still play the game, albeit much less than I used to. If the playerbase started growing again, I would be tempted to put more time in again. It's still a great game - it always has been.