In what way is it unbalanced? We also receive a fancy new codex every edition and in fact always receive it before BA does. BA also got no new models released with this codex so I don't think blaming it on that is fair or has anything to do with the event. Honestly, It just feels like we lack the player base we once used to have here on the forum and/or we have a large group of veterans who simply don't need many new models.
Well, unbalanced because both armies started in different positions, sorry English is not my mother language and maybe I'm not doing my best. I'm sure there are more BA players than Templars and sure that there are more BA in tournaments or casual games than BT.
Blood Angels have their own codex (BA+successor chapters), and they received special boxes (Primaris units and heros) with their heraldic, that is important for selling and increasing a fan base. Because you can buy Vainilla or BA or DA primaris, and then when Space Wolves will be released, I suppose they will receive more primaris boxes SW themed. So BA DA SW are the main SM chapters' ranges, and of course the vainilla range (being the BT and the other chapters "lesser chapters": White Scars, Salamanders, Iron Hands...).
Also they receive new fluff and they have more amount of fluff (in terms of volum/pag number, etc.) and received great amounts of stories like Devastation of Baal that is really important in the new background.
Black Templars in the other hand are in the vainilla codex (maybe the most divergent chapter in the codex) and didn't receive its own codex or "family codex" (Sons of Dorn codex), I think the main reason because we will never receive a "Sons of Dorn" codex is that Imperial Fists and Crimson Fists are codex chapters, but BT have similar amount of desviation and special stuff like DA for example, we are less codex compliant than them, and close to SW divergence.
We are in the same group than other chapters that are codex compilant, but it is true that it is a better position than most of them because we have 5 special units that allow us to play really different. We are not receiving new BT minis, but we receive all vainilla's ones so it is ok.
Another weakness is our fluff is really short and each edition is twisted... few days ago I started to read again the BT codex (2005)... there are many differences but our fluff is changing little bit codex after codex but not receiving enough love IMO.
I know there are other chapters in a worse position (Iron Hands), but I'm not complaining, I'm only saying that the most balanced competition could be DA vs BA. Another example could be doing a Imperial Guard competition: Cadia or Scions vs Steel Legion (also first rules in Armageddon codex), there will be less players with steel legion.
I'm sorry but the fact that there is a "BA" Primaris box doesn't really explain that for me. Those boxes literally have one tiny sprue of stuff with a few shoulder pads and an arm or two. That's it. It's not anywhere near the amount of stuff you used to get in a something like the old DA veterans box or the BT upgrade box.
Guys I get it, there are certainly plenty of good reasons why our showing hasn't been as strong, it's just... disappointing is all