HI Zag,
Why has God been choosing people for the past almost 2000 years and not others?

God's program is kind of like a Fortune 1 business. In this business He needs only so many managers and so many workers. The business won't really open for operation until the commencement of the next two eons/ages (the 1000 year eon and the new earth eon.

In that business we will have an administration:

Eph 1:10-12  to have an administration of the complement of the eras, to head up all in the Christ - both that in the heavens and that on the earth"  (11)  in Him in Whom our lot was cast also, being designated beforehand according to the purpose of the One Who is operating all in accord with the counsel of His will,  (12)  that we should be for the laud of His glory, who are pre-expectant in the Christ."

Notice what the business end of that administration is? It is to head up all in the Christ, both all in the heavens (not heaven but heavens) and all on the earth.

So God only needs so many people to be a part of that business.

We don't accuse Ford or Chrysler of wrongdoing for choosing just so many people to be in their businesses and neither should we accuse God of wrongdoing.

Ford and Chrysler try to choose the best. God does just the opposite. He chooses the worst.

1Co 1:26-29  For you are observing your calling, brethren, that there are not many wise according to the flesh; not many powerful, not many noble,  (27)  but the stupid ones of the world God chooses, that He may be disgracing the wise, and the weak ones of the world God chooses, that He may be disgracing the strong,  (28)  and the ignoble and the contemptible ones of the world God chooses, and those who are nobodies, that He may be discarding those who are something,  (29)  so that no flesh at all should be boasting in God's sight.

But this is not the end all of God's program.

Eventually the rest of mankind will come into the blessings of what Christ secured for them because He ransomed them too (1 Timothy 2:4-6). But the rest of all mankind don't really come into the blessings until the end of the ages.

There are three stages to God's program:

1Co 15:22-28  For even as, in Adam, all are dying, thus also, in Christ, shall all be vivified."  (23)  Yet each in his own class: the Firstfruit [class], Christ; thereupon those who are Christ's [class or group] in His presence;"  (24)  thereafter the consummation [class or group], whenever He may be giving up the kingdom to His God and Father, whenever He should be nullifying all sovereignty and all authority and power."  (25)  For He must be reigning until He should be placing all His enemies under His feet.  (26)  The last enemy is being abolished: death.  (27)  For He subjects all under His feet. Now whenever He may be saying that all is subject, it is evident that it is outside of Him Who subjects all to Him."  (28)  Now, whenever all may be subjected to Him, then the Son Himself also shall be subjected to Him Who subjects all to Him, that God may be All in all.)"

Spurgeon and Calvin's plan turn God into the most hideous monster far far worse than the pagan gods.
In their program God brings people into existence for the sole purpose of torturing them in flames for eternity. Some god, huh? Now that's the kind of god I can bow down with heartfelt adoration and worship with a loving, thankful heart! Not!
Spurgeon and Calvin's eyes were just not open to God's great plan of the ages, to head up all in the Christ and for God to be All in all.