Granted, we were chosen before the foundation of the world. But consider that God is creating our story. We are the hero of our own story. Our road to Salvation, we experience moment by moment and decision by decision.
Nevertheless, paying attention to verb tenses and temporal aspects of a Biblical text are among the demands of proper hermeneutics. When Paul says that Christ died while we were his enemies, he doesn't refer to any of us because we weren't alive when Christ was crucified. Paul isn't saying that we were reconciled 2,000 years ago, he is saying that there is no other person in all of creation that is the basis for our reconciliation. In short, Jesus Christ is the sole means for our reconciliation.
But we must all reconcile with God while it is still called "today."
I would disagree. We are not our own "hero": Christ alone is the "hero". We are but the recipients of what He, as the Savior, achieved on behalf of His chosen, and which, He freely bequeaths to them in its fullness at a time of His choosing. God knew before the foundation of the world, individually, whom He would save, otherwise, He couldn't have stated what He did Eph 1 and throughout all of Scripture.
In Romans 5 (and in prior chapters), Paul's purpose and focus, I believe, was to illuminate doctrine, not establish the timing of events. or the "temporal aspects" relative to those people to whom He was speaking. Were that his intentions, then the purpose of whole chapter would be devoted to, and limited specifically to them, and not be to teach the timeless full council of the gospel of God's salvation by His grace alone, and unworthy as edification for all of the Saints (remember God moved Paul to write what He wanted written and that was to illuminate His gospel - as established in Act 9:15 and Act 22:14-15, following).
I think this can be seen by the "Wherefore" in vs 5:12 which ties the verses prior to it with it and the verses that follow after it (5:12 - 5:21). They demonstrate that the full chapter is of one context and to edify of God's judgment and salvation.
[Act 9:15 KJV] 15 But the Lord said unto him, Go thy way: for he is a chosen vessel unto me, to bear my name before the Gentiles, and kings, and the children of Israel:
[Act 22:14-15 KJV]
14 And he said, The God of our fathers hath chosen thee, that thou shouldest know his will, and see that Just One, and shouldest hear the voice of his mouth.
15 For thou shalt be his witness unto all men of what thou hast seen and heard.