Could a loss of taste be the problem?

Two nutrients are implicated in taste/smell loss.
Zinc and Biotin. There are studies on PubMed where high dose biotin restored a patients sense of taste. This was in the 10-20mg a day dose range.

The problem with MEAL replacement is that calories are needed.
These are not easy to get in capsules and tablets. One huge flax oil capsule for example is one gram of fat....9 calories.

Any liquid is going to have a flavor added. You can get vitamins and minerals in tablets and capsules because they only need to be supplemented in small doses daily.

But MEALS require calories which is many GRAMS of volume and this is just not possible with pills. Carbohydrates, fats, and proteins are consumed in gram quantities to sustain life.
fats=9 calories a gram
carbs and protein 4 calories per gram

To get just 1000 calories which is a very low daily amount as you can see, would be a dunning task with pills.