“I tend to think that today’s apostles are what we call missionaries “
I understand what you are saying, but church planters are missionaries. They are not Apostles.
“The wall of the city had twelve foundations, and on them were the names of the twelve apostles of the Lamb.”
Revelation 21:14
Heaven has 12 foundations. One for each of the 12 Apostles. It does not have an ever expanding number of foundations to cover an expanding number of Apostles.
Your point is ludicrous. There were 12 original Apostles - after Judas betrayed Christ - then Matthew was selected to replace him. However, Paul, was also an Apostle, but not one of the original 12. The foundations of the New Jerusalem are in honor of the original 12 - all who died a martyr’s death - except for John. And, the Apostles planted churches - duh! We don’t find the word missionary in the Bible, but, their role is to evangelize and plant churches. Exactly, what the Apostles in the Bible did.