The voice acting community was criminally underpaid for a long time, and it became a somewhat "ruthless" practice to hire impersonators at even lower rates to get almost the same sounding voice. So voice actors developed an unspoken agreement that they would NOT directly imitate the voices of established voice actors to undercut the practice. If you did directly imitate, you had trouble getting jobs.
Eg, you could hire someone besides Kevin Conroy to do Batman, but the new person isn't supposed to try and sound exactly like Kevin Conroy (even if the studio pushed them to do so). Of course there's always quibbling about whether or not a voice sounds too similar, and the old "starving voice actor just needs to put food on the table" argument.
In any case Matt Mercer knows this, so there's some scuffle about why he imitated Jim Cummings so closely. And Jim Cummings didn't know about it / wasn't approached by Larian, WotC, or Mercer. Mercer himself has a lot of credibility so it's doubtful any harm was intended, but something happened there.
