Because the gold gods generally didn't see play, and when they did see play, they were barely able to turn into creatures in their games. Keranos sees play as a 1x SB card, but never activates. Pharika sees play as a 1-x mirror-breaker of sorts. The only two that really saw any decent play in multiples was Ephara, because her ability is nutty, and Xenagos back when R/G monsters was a thing. But even then both started disappearing from standard lists last season,.Why were the multicolor Gods "botches" at 7 devotion instead of 6? They of course would have been more powerful but a lot of them still saw moderate play and one less devotion needed wouldn't have saved the ones obviously not made with competition in mind (see Kruphix).
I will agree that Theros was the best set of that block and the follow ups on Monstrous and Devotion left a lot to be desired. Considering devotion stratgies were/have been doing well with pretty only Theros set with relevant cards there is an argument that the strategies may have become even more oppressive if good Devotion cards were printed in the last two sets.
I don't think Devotion needed the follow-up, it was clearly saturated well enough in the first two sets. The problem was with how everything else was handled-f or instance, BOTG clearly did not have enough mechanics playing in it, and JIN had too many.