Christ may indeed have eaten with (unrepentant) sinners at their table (in the hopes of convincing them to repent, as He Himself explains), but I don't recall Him inviting any of them to His, when He partook of the Last Supper, to which only His close circle of disciples were present, all of which have put their sinful lives behind them by that point.
The rules by which Jesus and Paul lived were different in many respects because Jesus was "born under the law" ("beholden to the Torah"):
[Gal 4:4 NASB] (4) But when the fullness of the time came, God sent forth His Son, born of a woman, born under the Law,
But Paul, because of the new covenant ratified upon Jesus' death, was not:
The tax gatherers eating together with Jesus were not (yet) brethren in a Christian sense.
And one assumes that, like Matthew, they were intent on not stealing in the future.
Separating from a professed Christian who deliberately continues in immoral behaviour is (clearly) quite a different matter.
Does Paul contradict Jesus by saying not to eat with sinners?
Paul did not say not to eat with sinners, the Greek word sy.na.na.migny.sthai (συναναμίγνυσθαι) rendered to "keep company" or "associate with "any so-called brother implies having a close fellowship or companionship and sharing with them the same views and Christian beliefs.
In 1 Corinthians 5:11, Paul addresses the command to people who claim to be Christians.
But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people.
Jesus ate with sinners who had not believed in ...
The operative word is ἄρχων (archón) meaning, "ruler", "chief". If I paraphrase BDAG, we have four types of rulers for whom this word is used:
Jewish leaders: Acts 14:2, 23:5, 13, 35, Matt 9:18, 23, 20:25, Luke 8:41, 18:18, etc.
Earthly, gentile rulers/authorities: Matt 20:25, Acts 4:26, 16:19, Rom 13:3, 1 Cor 2:6-8, Titus 1:9, etc
1 Corinthians 2:8
None of the rulers of this age understood it, for if they had, they would not have crucified the Lord of glory.
Noun - Genitive Masculine Plural
Strong's Greek 758: Present participle of archo; a first.
archón: ruler, chief
Usage: a ruler, governor, leader, leading man; with the Jews, an ...
It would help if the question gave specific verses corresponding to what is claimed in the question.
In fact, I don't see anything in 1 Corinthians 15 to indicate that Paul was talking about a physical resurrection.
A buried body is like a planted seed; what arises is not the original:
But some man will say, How are the dead raised up? and with what body do ...