Teams average 4 pitchers per game per team since 2015.

Major League Miscellaneous Year-by-Year Averages and Totals

https://www.baseball-reference.com/leagues/majors/misc.shtml

Pitchers/G

Since 1903 once it goes to the next integer, it stays there.

4: 2015-2026    12 seasons

3: 1990-2014    25 seasons

2: 1946-1989    44 seasons

Batters/G

Increased above 9.9 in 1953 ... and never dipped below 10 again.