It's interesting that it was noted the Cleric is a very strong class (on paper, at least), but then once Legends & Lore, Demihuman Deities, and especially the Forgotten Realms Faiths & Avatars and Powers & Pantheons came out, Mythos/Specialty Priests soon left the basic Cleric in the dust.
Part of it was, I think, that Complete Priest was the second Complete book, and they probably didn't have that good a grasp of 2e's peculiarities at that point.
For one thing, they classified the cleric's armaments as "good". Personally, I'd go with "medium". Yes, they have good armor, but only getting bludgeoning weapons is pretty weak. Good should be any weapon or armor, Medium should be either good armor or good weapons with mediocre in the other (like the cleric or rogue), and Poor should be mediocre in both (like cleric weapons and rogue armor).
For another, they treat every sphere as being equally valuable. Astral, with IIRC two spells at level 5 and 7, counts the same as Combat which is where the nice buffs are IIRC.
And third, they are drastically overvaluing having breadth of spell access. A priesthood with Good combat abilities should, IIRC, have major access to two spheres and minor access to two more. As I recall, it's kind of rare for a sphere to have more than two, maybe three, spells per level, and there are plenty of cases where levels are entirely blank for a sphere. So call it an average of 2 spells per level (which I think is overstating it), and you get a total of 8 spells per level for levels 1 to 3 (or was it 4? I think 3 was minor sphere access and 4 was Lesser Divination, but I could be getting those confused and can't be hedgehogged to check) and 4 per level for 4 to 7. That's pretty disappointing.
Plus, they are ignoring the role of the cleric in the party. Their job is to be the healer. You can go "but why should a priest of Thor be healing instead of casting lightning bolts?", and that's a fair question from a world-building perspective. But the party needs a healer, and if the priest of Thor can't do that then they can't fulfill the cleric's role.
I think 3e actually had the right idea with giving clerics a core spell list and having a small number of bespoke-ish spells on top of that based on domains. I think it might be tuned a little too much toward homogenization, but more or less having the right idea.