Not many other options.
It wasn't that noticeable because the team was winning (mainly because the pitching, defense and the top 6 hitters; Lindor, Ramirez, Edwin, Bruce, Santana and Jackson were all producing), but the Indians weren't exactly a beacon of health or certainty coming into this series, particularly in the outfield.
Zimmer goes down for the season on 9/10. Guyer goes down for the season on 9/14. Both of those guys were definitely going to be on the playoff roster. So that gave the Indians two less options in the outfield.
The fallout from that is Kipnis not only having to move to the outfield, but having to start in CF. He clearly doesn't have the range or the arm to play there and he only had 33 at bats from August 23rd until the end of the season. Not only was he out of position, but he simply wasn't ready to play either.
On top of that, with Zimmer and Guyer down, that meant Brantley and Chisenhall both made the roster. Brantley had all of 3 at bats since August 9th and clearly wasn't ready for playoff pitching. Chisenhall basically the same thing. Missed six weeks, came back for two and didn't hit at all, then missed another two weeks and ended up only having six at bats total in the three weeks leading up to the playoffs.
So you add all that up and now you have three guys in Kipnis, Brantley and Chisenhall all on your roster of 14 guys that for all intents and purposes are automatic outs. Toss in Double A outfielder Greg Allen who only made the team for pinch running and defensive replacement purposes and now you have four automatic outs out of 14.
Now we go a little bit deeper. The main reason why they moved Kipnis to the outfield instead of just playing Chisenhall or Jackson there (or biting the bullet and just starting Allen) is so they could have the best infield defense possible. The problem with that is that that meant Urshela starting at third base and it's abundantly clear he can't hit bad MLB pitching, much less playoff pitching. So now five of your 14 hitters are guys that we've established can't hit.
The curious decision to bring Gonzalez and not Diaz = a 6th player out of 14 that can't hit.
So now, through injuries, they've set up a situation where 42.8% of your playoff roster simply can't hit. That makes the margin for error nonexistent. You get one injury and your only solution is to bring in an automatic out from the bench.
You get other guys that were hot down the stretch that start scuffling like Lindor, Ramirez and Jackson did, and the rest of the roster just isn't able to pick them up.
Now all of these problems existed the last month of the season, but they basically didn't matter because the top 5 hitters were all on fire, the defense was top notch and the pitching, both starting and relief, was the best in the league.