Colony drops = First Gundam
Masked man = First Gundam
Colonies infiltrated and/or destroyed = First Gundam
Teenage boy stumbling on Gundam and becoming an ace pilot = First Gundam
Cilvilians and children being brought aboard a Federation battleship = First Gundam
Psychic abilities of pilots and people in space = First Gundam
Haro = First Gundam
If you're seeing some sort of theme or action consistently across Gundam titles, it's a safe bet that it was established in First Gundam. Maybe Zeta with the alternate identity and sunglasses.
Those
young whippersnappers who haven't seen MSG 0079!!! When I was your age.....
*yells at the cloud*
Seriously though, the essence of what makes a Gundam show a Gundam show is so potent that they could just rip it off wholesale with just a few adjustments to the era, the archetypes and it'd still be great. Probably deja vu overload for the vets who've been around since 0079. Honestly, if you were a kid in '79 when the 1st Gundam came out and are stll an ardent follower of the show you'd have to be in your late 30s, early 40s by now lol.
Gundam GAF's probably not that old on average lol. Most probably picked Gundam up for the 1st time with SEED in the early 2000s and followed the exploits of 'Jesus' Yamato and 'Mary Sue' Lacus. So it's quite understandable that they'd assume Origin copied SEED. You can see the fanbase divide very clearly on GundamGAF, between those who think U.C. is the end all, be all (my crusty old self included), and the others who prefer the post U.C. series.
The U.C. fanbase had been waiting for a revival of that golden era for the longest time, and it was great that the showmakers decided to bring it with Unicorn, which is the best thing to occur in recent Gundam history for the longest time.