I like it, and I think it was necessary. I agree it could have been slightly more decorative, but I think it's okay that not everything is a shrine. If this kit was as over the top blinged out as the Exorcist and the Immolator, those kits would be less special by the comparison. We see this with the Sisters Rhino too. And I think it's appropriate to have the possibility within the range to depict a different feel to the army.
I've seen more "military" looking forces represented before, and while it isn't the way I see sisters, I think it's valid. These are guys who, for decades have been swapping out pipe organs for whirlwind launchers as an aesthetic choice; there were a fair range of opinions on the stained glass Immo turrets, and some folks sought different options there too. Like I said, I personally prefer over the top baroque too, but I like that the range is nuanced enough to afford other possibilities.
As for the Trinity:
I like it, and it's fluffy. I am wary of the slippery slope that could erode a core concept if not kept under control. Upgrades to the Heavy Bolter helped us somewhat in that regard, giving us some firepower from distances > 24". But that's still only 36". Until this tank, we've had 1 option with a greater threat range than 36"- two if you count single shot HK Missiles. I just feel like that's a little limiting to a military force, and I think it's good to have one more tool in the toolbox.
As for the Repressor:
I like it too; I had expected it. But I think that Melta is so good in the current meta that Repressor Rets and Doms with melta would displace every other vehicle choice, and that mobile Melta spam would become the most hated thing in the edition. I think this tank may do more for the army in terms of diversifying available options.