I think one of the reasons the 70s UNIT era managed to feel so much more anti-militery than the current depictions of unit, apart from the Doctor's interactions with them as he has way too much trust and faith in the current unit, is that Kate has so much more power than the Brigadier ever did.
Currently (I haven't watched twbtlats, this is just from the main show) although Unit's funding is dependant on public opinion, Kate has a ridiculous amount of power when it comes to getting not only the British government but also governments all over the world to listen to her and accept her being in charge in emergencies.
With the Brigadier on the other hand, he may be in charge of Unit but so much of his role in the 70s stories is
a) trying to convince the higher ups to either take action, or not take action, and he very rarely succeeds. Or
b) trying to assert Unit's authority as an international security force with emergency authority over local/national governments and also failing often due to legal technicalities or again orders from higher ups
The Brigadier is usually focused on saving civilians and can pretty often be (eventually) persuaded to consider the aliens' side or to stop or at least delay violent action.
The show isn't depicting the Brigadier as being evil for being part of the military, instead it's very cleverly depicting the military itself as being bad by showing the Brigadier as a (mostly) good character, but due to being in the military is both unable and also unwilling to disobey direct orders from those who do want violence.
So many things could have gone better if the Brigadier was ever willing to disobey orders he disagrees with, but he's not, even for the sake of the Doctor and even when presented with all the logic of why he should, and why it would save lives. He'll try literally everything he possibly can to change the minds of those giving orders, or find loopholes, but at the end of the day, he's a soldier and he'll follow orders.
That's why it feels so much more anti-militaristic despite Unit being some of the main protagonists because it depicts the military itself, and the obedient mindset of those in it, as the bad guy. And it's pretty clear that when the Unit protagonists have to obey orders because they're in the military, it's a bad thing!
Present Unit on the other hand feels more like "sure they still mess up occasionally but look! Now the Doctor has an army and soldiers on his side, who have power over all governments, making it much easier for him to win! This is a good thing and the implications and ethics will not be explored!!"
