Looking at the depth chart the M's have MOST DEFINITELY improved their depth. It's one thing to read it and believe it, but when you look at the graphic the M's are deep at every position in bona fide big leaguers. No more hoping some kid can be a starter or cut it if one of your starters goes down.
The lone exception is Ketel Marte. If he doesn't cut it as a starter, you can be the M's will be working on a trade or signing. I doubt anyone here harbors serious doubts that Marte can at least be serviceable on both offense and defense, and we expect him to be more than that.)
This depth extends to the starting rotation as well.
Regarding the bullpen, I suppose if you consider stringed pasta to be depth then the M's have it there too, but again, the M's can react if the pen becomes a serious problem.