Here's the same rolling data for his 3FG:
2023

2022

2021

2020

2019 (shortened season)

2018

2017

OVERALL

So the 3FG tells a slightly different story - his 3FG has gone from mid 40% in his rookie season, where he was in the top 4$ in the league, to the 35%-37% mark the past 3 seasons, where last season he was in the 59th percentile in his position. His eFG has remained fairly constant around the mid-50% mark, so as his 3FG% has gone down and his FT% has remained constant his 2FG% has gone up, from below 50% to early 55%. So it suggests as he has gotten older and bulked up, he has lost a bit of his outside shooting touch but, as @celticinorlando said, he is more able to drive the ball and score inside. That's my totally unscientific assumption based on the little bit of data that we have. I don't think it's anything to slit wrists about however 
TP for this.
Also, a few other points.
1) He is being guarded MUCH more closely around the 3 pt line since his rookie year.
2) His assist numbers have been steadily increasing each year, with a new high average peak in this year's playoffs.
3) Over 90% of his 3 pts made in rookie year were assisted. This year? Less than 50%
So, in conclusion, Tatum just may not be a super gifted pull up 3 pt shooter, but he is smart enough to realize he needs to drive hard and dish.
The real test will be if he can increase his assist numbers, and now with Jaylen going supernova and everyone else being elite shooters, maybe he will have more catch and shoot opportunities next year.