Question marks, sure, but Buxton is your best bet in CF right now. He's not getting replaced before 2019. Same for Sano, really, although it might not be at 3B.
3 of the guys you mention replacing just signed here on fairly cheap 1 year deals. I think those positions are easier to address in free agency. (And we may have enough pitchers to not worry too much about further external replacements, especially considering we have team options on Santana and Rodney.)
And we're flush with cash after the season. We can easily re-sign Dozier and/or Escobar if we want too.
What is your plan for 2019 at catcher? Here are the potential free agents:
Drew Butera (35)
Robinson Chirinos (35) — $2.375MM club option with a $100K buyout
A.J. Ellis (38)
Tyler Flowers (33)
Yasmani Grandal (30)
Nick Hundley (35)
Jonathan Lucroy (33)
Martin Maldonado (32)
Jeff Mathis (36)
Brian McCann (35) — $15MM club/player option
Devin Mesoraco (31)
Miguel Montero (35)
Wilson Ramos (31)
Rene Rivera (35)
Kurt Suzuki (35)
Matt Wieters (33)
Note this also suggests the Dodgers, Astros, Nationals, Braves, etc. could be looking for catchers too, so there would be competition.
Let me throw a hypothetical example of what I'm talking about. The purpose isn't to discuss the hypothetical names chosen at the granular level because I have no idea how much a free agent will cost or what teams will give up what players.
This is for a broad sense of how the resources it would take to acquire Realmuto could provide more bang for the buck. I'm not taking the time to research how many years of control or salary for this exercise. This is just for a general sense.
Castro (If Castro can't play - Get Mathis or the Best Defensive guy you can find)
AAA Depth: Best AAAA Guy you can find.
Mauer (Or FA Matt Adams if Mauer retires). Matt Adams can also play a little OF on occasion.
Eugenio Saurez (Trade with the same pieces it would have taken to trade for Realmuto... They take the prospects and replace him with Senzel).
Sano - Can play 1B-3B-DH (Let him compete for the Lions Share of playing time.
AAA Depth - Kennys Vargas or someone like Mark Reynolds.
Eduardo Escobar (Please bring him back... whatever it takes... He is capable at so many positions)
Jurickson Profar (Free Agent Signing) Multiple Positions... Can also play OF.
AAA Depth: Nick Gordon
Reds OF in the Suarez Trade (Duvall or Schebler)
AAA Depth: Lamonte Wade
Do not sign a dedicated DH... The DH spot can be used to get the extra bats in the lineup instead of a guy like Morrison who is 1B only clogging things up.
Now... This is just a quick example of what can be done to build depth and provide insurance in case any of the players are playing like Buxton, Sano and Morrison have been playing this year.... you are also protected against injuries should they occur and they do. You will have honest to god competition at all positions.
A good manager will manage the playing time obviously but a good manager can find a way to do it based on Hot/Cold and Matchups or gut... Like Maddon does, Like Roberts Does, Like Hinch Does, Like Martinez Does.I'm not sure that Molitor is that guy but he won't have to tolerate a sub-par performance anywhere with a roster like this. (Besides Catcher of course).
You might be able to spend a little more on a Catcher if you'd like and you have money left over after addressing the Bullpen.
Here's a sample lineup:
Kepler - RF
Escobar - 2B
Saurez - 3B
Rosario - LF
Sano - 1B
Adams/Duvall - DH
Polanco/Profar - SS
Garver/Castro - C
Buxton - CF