Well, lets break this down a bit further.
First and foremost, what do you think an established game looks like? Is it the size of the player base or maybe presence on the E-Sports scene? This type of information would be helpful in making more realistic estimations of how Supernova is either meeting or failing expectations.
The player base is being kept intentionally small at this point. The game isn't being actively advertised outside of very select outlets. Bandai has mentioned many times before that they will begin an active marketing campaign once open beta begins. Partly because this is also when they plan to begin localization. Part of the issue with players is that they are experiencing very high ping and severe lag. This is purely because there is only one server handling matches located in New York City. A lot of players, at least in alpha, stopped playing because they literally could not play the game. So, the player base will grow just not on our time table.
As far as the number of commanders, I'm fine with it. League has a growing roster of Champions, but it has often lead to some of their initial creations losing viability and requiring very extensive reworks. I mean, Poppy was one of the first release champions and its been over 6 years. I would much rather have a smaller pool of commander who are well thought out and developed then have only half of them still useful a year or more after release.
Smite and HoTS are probably not the best comparisons either. Smite bases all of its characters off of mythological gods, giving them a lot of reference material to guide their design. They still have to make it unique to their game, but it helps when your characters have had centuries to be developed and refined. HoTS, to me at least, is a repackaging deal. They take some of their established characters and make the into MOBA appropriate versions. I'm sure it still takes effort, but as a whole it seems rather uncomplicated.
Supernova is creating a unique world and story. They have to create the mythology of this universe and find where their characters fit it. As such, its going to take more time and effort for them to develop entries. And while I may not like it, I appreciate the attention to detail.
I don't think talking about making the game established helps unless details on how to do that are provided. As you mentioned before regarding Dawngate, player base isn't necessarily a marker for an established title. And to be honest, this game isn't ready for a competitive scene just yet. Adjustments need to be made to the item system and commanders before they're fully ready for an honest ranked match up.
As a side note Dawngate has a "spiritual successor" in the form of Spiritgate. Granted its a DoTA 2 add on, but its something right?