Of course above all there is one thing we all need to remember.
The year is 2005 CE (Common Era, not Cosmic Era). What ever technology we see in Gundam obviously far surpasses anything we have today (Luna-Titanium, Neo-Titanium, Phase-Shift, beam weapons, etc), so of course a modern day mech wouldn't be too useful in combat. Same with Macross, we don't have an SDF-1 to reverse engineer.