Well, we did have L.EG.I.ON. which served pretty much that purpose.
I mean, seriously, of all the planets in the 30th (or 31st century now), only Earth is present and inhabited in the current day? When we have planets like Rann, Thanagar and the Vega System all populated?
Speaking of which, I also found it a bit annoying that Rann, Thanagar and the Vega System were left almost untouched in the Legion. As if they were afraid of tripping up writers from using those planets in the modern day setting. When Earth is the planet that sees the most action and is constantly being threatened? Yet, it does still exist in the 30th (or 31st) century?
I guess that allowed writers the possibility of destroying Rann, Thanagar or one of the Vega worlds without contradicting something written in Legion... but still, if Earth could survive another thousand years with far more constant threats (on a yearly basis, no less), why couldn't they?
The lack of non-Earth planets being shared in the present and future added to the sense of disconnect.
And 1000 years is a long time. You could have the Legion visit Rann with absolutely no mention of Adam Strange, because no one on the planet would even remember him. And if, by chance, someone did they surely wouldn't know the finite details of his life that could compromise any stories still being written.