This particular verse can see be seen in a much clearer light if properly translated.
Youngs does a better job of translating this verse:
First, a short background to bring in a better context of the scripture as well. Acts 17:1-9 shows some of the afflictions and persecutions the new believers in Thessaloniki were experiencing and from who.
5 The Jews, however, became jealous. So they brought in some troublemakers from the marketplace, formed a mob, and sent the city into an uproar. They raided Jason’s house in search of Paul and Silas, hoping to bring them out to the people. 6 But when they could not find them, they dragged Jason and some other brothers before the city officials, shouting, “These men who have turned the world upside down have now come here, 7 and Jason has welcomed them into his home:
They are all defying Caesar’s decrees, saying that there is another king, named Jesus!”
Acts 17:5-7, BSB
"These believers were experiencing the wrath and anger of men and thought God was against them. After all, God wasn't doing anything to stop it. These believers however grew in endurance and faith and Paul makes a statement to encourage them." From Concordant Commentary
That is why we boast among God’s churches about your perseverance and faith in the face of all the persecution and affliction you are enduring. 5 All this is clear evidence of God’s righteous judgment. And so you will be counted worthy of the kingdom of God, for which you are suffering. 6 After all, it is only right for God to repay with affliction those who afflict you, 7 and to grant relief to you who are oppressed and to us as well. This will take place when the Lord Jesus is revealed from heaven with His mighty angels 8 in blazing fire, inflicting vengeance on those who do not know God and do not obey the gospel of our Lord Jesus. 2 Thessalonians 1:4-8, BSB
So God is going to bring about his righteous judgment between the believers and the unbelievers when the Lord Jesus is revealed from heaven.
The Jews who were causing all of this will suffer ruin and loss for a complete age. It's not eternal and it's not extinction. It is a loss for a very long time. Even though they have been persecuting these believers for a comparatively short time, they will be put away from the Lord's presence for an age, which is a considerable amount of time.
who shall suffer justice — destruction age-during — from the face of the Lord, and from the glory of his strength, 10when He may come to be glorified in his saints, and to be wondered at in all those believe. 2 Thessalonians 1:9-10, YLT
Here are two definitions, first for "age," which is commonly mistranslated as "eternal."
166. aiónios ► Strong's Concordance aiónios: agelong, Definition: agelong, eternal Usage: age-long, and therefore: practically eternal,
unending; partaking of the character of that which lasts for an age,
as contrasted with that which is brief and fleeting.
The second one is for "destruction," which does not mean "extinction."
3639 ólethros (from ollymi/"destroy") – properly, ruination with its full, destructive results (LS).
3639 ólethros ("ruination") however does not imply "extinction (annihilation). Rather it emphasizes the consequent loss that goes with the complete "undoing."
To sum it up, God's righteous judgments are always corrective, and, in this case, the judgment will show in time who the true believers are and who are not. The believers will be glorified, and the unbelievers will suffer loss for a long time. They will see that they missed it and that they were in the wrong.