I've pointed before that there is a problem that has developed with the character and his positioning, by both creators and editors, since the 'Rebirth' relaunch. It lies partly with both the attitudes and creators we have currently being rigidly ingrained with the thinking and ethic of the post-crisis landscape of the DC Universe, with its reduced levels of power and aptitude for their frontline heroes, and additionally lies with the move to marry that post-crisis with the better aspects of the pre-crisis.
With Superman we see an uncomfortable attempt to balance these aspects - he is presented as scientifically gifted, yet seldom exploits this intelligence. We see hints (as with General Zod and his family) that he may well be capable of interplanetary flight under his own power, yet it is yet to be confirmed as a fact, much less exploited. Much of his earlier years and life in Smallville are yet vague, some elements have suggested he was never Superboy for example, but what is fact?
And yet perhaps the simple truth to the vagueness of his ability for deep space travel under his own power lies in the simple fact that the publisher is forcing him to adhere to strict newtonian physics. Hence even if he, or Green Lantern for that matter, is capable of flight at speeds of 25 times lightspeed... that is still a speed which is insignificant on the galactic scale.
The reason Superman needs Green Lantern to open a pathway to OA just this week isn't necessarily that he couldn't get there under his own power, rather that it would take far far too long for him to do so!
This obstacle called physics is not a new problem. Even in the bronze-age there was a noticeable shift in how Superman's trips into deep space were undertaken, as more and more the depictions would make the point that to do so he would either detect a convenient spacewarp, or use hyperspace, as under his own power the journey would take far far too long. If indeed it was possible at all... so in a sense the differential between the Superman of then, and the Superman of Now, is that today's Superman has no such convenient cosmic gateways by which he can access. Not under his own power and initiative.
But as I say some middle-ground could surely be found, one that would satisfy and balance the need for character limitations, and the requirements for a wider range of storytelling options to be made more readily available. As here in 2017 it s becoming more and more the case that Superman as a character, and pre-eminent SuperHero, is all too often an awfully limited and constrained figure for what he is.
I would like DC to just give to us the Superman who can travel FTL while in outer space, and have it explained that he can do those things due to the fact that he can somehow manipulate energy /matter without being aware of it, in order to obtain "earp speed"
They have shon him able to conatin a minature black hole, and lift planets still, so why not be able to also now do that?