"UEF has worst land scouts."
They have some advantages to the others. While you dismiss their extra DPS, it means they can kill enemy land scouts and radar much faster. Personally I prefer them to selens because they have better radar range (which is why I build land scouts) and are much cheaper. Spirit's by far my favourite scout though.
"T1 bots...the only scenario where comparably good DPS and speed matter is when raiding poorly defended structures or attacking units that have no ability to defend themselves against land attacks"
The main use case for T1 bots (with the potential exception of the flare) is to attack units that cant defend themselves (engineers), so speed is very useful
"T2 heavy tanks: UEF Pillar...Why does it have the lowest amount of HP...Does it really tie well into UEF doctrine?"
Compared to the other factions' tanks the pillar has more health per mass cost so you can still argue it fits with the UEF doctrine (i.e. a UEF T2 tank army will have more health than a mass equivalent tank army from another faction).
"UEF Parashield is straight up worse than Aeon Asylum" If UEF's slight faction identity is units that are generally 'tankier', Aeons is its focus on shields (shield instead of nano for its ACU, shielded T2+T3 tanks, T2+T3 shield generators that focus on health over size), so it's reasonable to me that the 'shield' faction has a stronger shield.
(Titan+Percy - others have already covered)
"UEF Fatboy is a very weird and too much of a situational experimental compared to something like Cybran Monkeylord"
It's relevant for longer in the game than a monkeylord which is usually good as an early experimental and/or to try and surprise the enemy. If you can protect it from air and TML snipes then it ends up being quite a good value over time unit, and can force the enemy to either retreat to T2 arti, or push in (so provided you have enough percies supporting your fatboy that can be good for you). It's not that strong, but it still has a use.
"Tier 3 stationary shield generator" - Seraphim costs the most but yeah generally Seraphim has the best shield, and then the other factions have different focus (UEF on size, Aeon on strength, Cybran has the worst shields but at least have a very cheap t2 shield which also has use)
As to whether units follow the suggestions of a UEF doctronine/faction focus, agreed there are some exceptions.