1.During night,too? and, both loitering ammo and racing drones could hide almost to last moment before attack.Not mention,they could attack in swarms.
Even more so at night. Fuckers with some training can give Astartes a run for their money in perception, agility and reflexes.
2.They had 1 Astarte for one planet - not enough to deal with it.Not mention,not all xenos are idiots like orks.
Pointless soundbite. Most planets aren't in a serious war at all times, nevermind in wars that require Astartes. Its just like saying that USA can't use F-22's to deal with things because they have way less than 1 per city.
Not all xenos are orks, but not all xenos are fighting Imperium at all times, while orks outnumber all xenos except for Tyranids (and that one is a maybe), and very much love picking fights.
3.Servitors too costly? brainwash them,they would be no more costly then average IG.
Servitors need maintenance, they are biological robots. IG can take care of itself, servitors need a low level tech for that, and sometimes a techpriest, just to not rot away.
4A.No,IG is not soviet army in space,they were semi-competent.They are soviet army parody in space,or current kgbstan forces from Ukraine.With such army,IoM should cease to exist.
They kinda are. They have some competent units with good equipment, but many others are glorified WW1 troops with lasguns, and some crappier units don't even have normal lasguns.
Of course they don't use those crappy units to assault Tau mechanized divisions, but for example to hold off orks or pacify some feudal world rebellion.
4B then they should cease to exist as state,becouse even if orks and Eldars could not innovate,some Xeno species/or lost human colony/ would wipe out them long ago.
How hard is it to understand that they have Astartes, Inquisition, AdMech, and Navy to deal with those rare scenarios?
They use the same weapons for last 10.000 years - if we did the same,we would fight with stone age weapons.
The knives we use now aren't meaningfully better for stabbing people than the ones they used 1000 years ago. The hand grenades and similar explosives we have now are maybe 20% better than the WW2 one. Many weapons hit diminishing returns in technology badly.
They have weapons way beyond what we have now, but most of those aren't for IG.
Even on our planet it is not possible,somebody would innovate,and others would either innovate or die.
AdMech has monopoly on that and sometimes does... just very slowly.
5.Not every dyvision fight ships,but every dyvision fight enemy army.Even polish army now could do that.
And not every division needs long range artillery. For example some more mobile US and UK units stick with 105mm artillery. That goes double in 40k where most armies don't have even that. So they could come to a conclusion that in the rare cases where the enemy has a lot of very long ranged artillery good enough to snipe theirs, they can relatively easily use the giant macrobattery guns they have on most starships with shells the size of a tank that can reach anywhere on the planet not covered by a shield to suppress it.
If your army need help to fight enemy armies,then they are not army.
And Your country would cease to exist,unless there is no other countries.
It's like saying that US Army is not an army because for some fights it needs the Air Force or Delta Force to help, you are making up bullshit rules no one cares about as usual.