Mmmm not sure that's true.
Granted, it DID get a bit wibbly wobbly timey-wimey there... but honestly it's pretty easy to wrap your head around it IF
1. Loki's 2012 escape is accounted for in his Disney+ series, and THAT stone gets taken back to SHEILD of 2012 by someone, eventually. Otherwise, there's an alt dimension with no Space Stone.
2. Tony's snap was largely dramatic, and the "dusting" was just HOW the Army was sent back to 2014. This would include Nebula 2014 being repaired, ALL their memories being wiped, and Tony leaving knowledge of himself in Thanos's mind. I could see Tony doing that, he's through AND sarcastic. Otherwise, there's an alt dimension with no Thanos. HOWEVER, this doesn't account for Gamora 2014 that we might find running around in the future of the MCU.
What we don't know, even now, is how Thanos knew about Stark. We can assume Thanos learned about Stark in 2014, but that Thanos ended up dusted in 2019. WOBBLY!
3. Steve's adventures in the past are funded by extraordinary amounts of Pym particles and equipped with a shrunken toy Benatar. Given enough Pym, Stark, Banner, and Guardians tech, Steve could EASILY accomplish the return trip(s) to all stone locations, AND find his way to Peggy in 1950.
Of the above, I think Option 2 is the wobbliest, and could result in an alt dimension problem if we discover Gamora was spared and Thanos 2014 was wiped out.