homages to non MCU movies (spoilers)
The way they go back in time in a circle - Timeline (the end with Cap was also similar to how TL ended)
Time travel interacting with previous movies/events - BTTF2, Terminator 5, Star Trek VII (had a similar plot to IW/EG with the villain successfully carrying out his universe ending plan despite Picard and Co and then the time travel reset/sacrifice death of the iconic lead)
time travel plot of altering the timeline after apocalyptic world ending event - XMen DOFP (also set 2023), Star Trek IV
reversing time to bring back the dead - Superman 1978, Masters of the Universe
Going back in time to grab the McGuffin to bring back to use in present - Star Trek IV
All powerful villain who wants to destroy humanity via timetravel – Star Trek First Contact, Star Trek 2009, T2 etc (also Thanos = XM: Apocalypse/Dark Phoenix)
Returning back the moment you left - BTTF, Star Trek IV
Tonys death/goodbye scene - very similar to Ben Stiller in Tropic Thunder (as RDJ watches)
timemachine built into old vehicle - BTTF
character decides to stay in the past and finds himself more happy there - BTTF3, Timeline