Hitting a baseball in the majors is harder than ever. Batters in the first half of last century didn't have to face integrated pitching staffs or fresh arms throwing in the 90s coming out of the bullpen at night half the time. There were no such things as analytics departments breaking down video or check-the-check.
Anthony looks great, a guy who can work a pitcher and slug a pitcher. He also struck out about 6 times every 20 at bats. As for another tall lefty swinger, the MLB's all-time On Base leader -- Ted Williams (career .482) -- in 19 years, for every 20 ABs, he struck out... once.
For a more recent comparison, here are the Red Sox' two best homegrown players this century, who both debuted at age 21:
Mookie Betts...........291 BA in 52 G, 5 HR, 18 RBI, .368/.444/.812, 14.6 K-rate, 2.3 WAR
Roman Anthony: .292 BA in 71 G, 8 HR, 32 RBI, .396/.463/.859, 27.7 K-rate, 3.1 WAR
That's encouraging... and he's extended.