Darkness (as in, the spell) explicitly prevents seeing *through* it, not merely into it.
If you wish to take that interpretation, then you are forced to say that creatures without darkvision CAN see through it... since the sentence only explicitly references creatures with darkvision. That makes very little sense and is obviously not a correct interpretation. If you want to say that creatures without darkvision also can't see through it, then you are making a logical jump - an assumption, or extrapolation, which invalidates any ruling you arrive at after that point; 5e philosophy is based around two basic precepts: "The rules do what they say, and not what they don't say" and "Specific beats general". This leaves no room for extrapolation or logical assumption, except as house rules.
That sentence in the spell is specifically calling out a "specific-beats-general" overruling of the darkvision trait... that is ALL it is doing. It doesn't reference creatures without darkvision, because it does not change the general rule for them in relation to darkness.
No part of the spell says that light cannot pierce it; it says that light cannot illuminate it. These are different things. If light could not pierce the spell, it would say so. That light cannot illuminate the spell area simply means that if an area of dim or bright light overlaps with the spell's area, it fails to illuminate that area - it remains dark. That is all it means.
The darkness is magical, yes; the spell then defines the ways in which it is magical. Those are the only ways in which it differs from mundane darkness. If it differed in any other way, the spell would say so.
The only way in which the magical darkness differs from mundane darkness are spelled out in the spell: creatures with darkvision still treat seeing into the area as full darkness, and mundane light, as well as magical light level 2 and below, cannot illuminate the space that it covers - it remains darkness, and overrules such attempts at illumination. Those are the only ways in which it differs from regular mundane darkness. If it differed in any other way, the spell would say so.
So if you're standing inside of the spell's area, your eyes cannot pierce the darkness with mundane sight or darkvision, it is effectively opaque.
This is untrue. Nowhere in the spell, or in the rules for light and darkness, is this said. If it created a magically opaque space, it would say so. It does not. If the blind condition came into the ruling of the spell in any way beyond the normal rules for light and shadow, it would say so. It does not. You are extrapolating to the idea that you can't see out of it; that is not part of the spell or the rules for light and darkness. That makes it a house rule of yours. As I pointed out previously, vision and targeting in 5e is always about what you are trying to see, not where you are looking from. The rules regarding darkness and vision support this: they explicitly call out the difficulty it causes when trying to see a creature that is IN a heavily obscured area... and explicitly do NOT say anything about impairment when attacking out of heavily obscured areas, such as magical darkness, which is used as an example along with dense foliage (If you were impaired when trying to attack out of a heavily obscured area, then ambushing anyone, ever, would be impossible).
Darkness itself has a recorded effect: it is heavily obscured, which is defined with the effect that creatures are considered blind for attacks they make when trying to target a creature within that area. A creature outside the darkness trying to a target a creature inside the darkness, then, is considered blind for the purposes of attacking that target. Two creatures within the magical darkness trying to attack each other are both unseen attackers by the other (due to being in a heavily obscured area), and blind in terms of trying to attack each other (trying to target a creature that is in a heavily obscured area), so they both go to straight rolls. A creature inside the darkness trying to attack a creature on the outside, that is not in a heavily obscured area is not impeded; if they were, the rules would say so. They do not.
The rules do what they say, and not what they don't. Anything else is house-ruling. Which is fine, incidentally; what matters is that your table agrees with the interpretations and that your table is having fun... But I'd prefer to see video game interpretations using the written rules.
IF darkness behaved as you're implying (and, I concede, as a very large number of people do seem to erroneously interpret it), then there functionally is no way to use the spell without always shooting yourself in the foot. It would be *especially* useless for drow, who have historically used the spell as part of their assassination tactics and politics. Do you feel that that is the intention? If it effectively renders anyone interacting with it in any way, in or out, from within or without, blind, then the spell would be a very stupid and ridiculous spell, and wouldn't ever really serve to benefit the user (with the solitary exception of devil's sight warlocks.... and then only by virtue of allowing them and only them to ignore its effects). Do you actually believe that that is how the spell is supposed to work? That someone would write the spell with the design intention of doing that?
((Last minute edit: As an extra example to back up my point about the way spells and rules do what they say and not what they don't, compare Darkness to Hunger of Hadar: Hunger says "[...] No light, magical or otherwise, can illuminate the area, and creatures fully within the area are blinded." Hunger explicitly notes that creatures within its darkness are blinded. Darkness does not. If a creature within the darkness created by Darkness was blinded by being in it, the spell would say so.))
