Bumrah's lack of wickets relative to his age completely rules him out of the ATG debate in Test cricket. The fact that he was not good enough to play for India at an age where the aforementioned bowlers had already a similar number of wickets that Bumrah does now counts against him, and it is no one's fault except his.
The difference between Steyn and Anderson is that Steyn himself has 400+ wickets and when both him and Anderson were playing in their prime, there was a huge gap (7-8 runs) between their respective averages.
When we talk about Bumrah in Test cricket relative to Rabada and Cummins, 170 odd wickets at 20 is by no means better than 300 wickets at 22. The gap is clearly not significant at all and therefore, the massive difference in the wickets tally makes a difference.
Steyn at Bumrah's age had 300 wickets as well. A fast bowler with only 170 odd wickets at the age of 31 is a fighting a losing battle against time. Even if he ends up with 300 wickets, he will have pretty much the exact same record that Cummins and Rabada do today, and by the time Bumrah gets to 300, both of them would have crossed 400 at roughly the same average, so Bumrah is clearly not better than them in Test cricket.
Bumrah is undoubtedly India's GOAT Test pacer, but that says less about how good he is and more about how awful India's pace bowling legacy is, because prior to Bumrah, their best Test pacers to date wouldn't even carry drinks and towels for an all-time D XI. However, if we look beyond the prism of India, Bumrah doesn't even enter the ATG debate in Test cricket because there countless pacers with a superior legacy in the format.