Yeah, having an insert, i'll never buy another insert again. Everything about it is more difficult, more expensive, less producing, and leaves you no fireplace when the power goes out taking away the option to burn wood.
They are not for everyone and you are correct the nature of them is you have to cram everything from a free standing stove into the space of a fireplace. In doing that motors get smaller, fans are never as easy to access and are usually noisy. The pellet hopper is never as easy to fill....
The benifit is you utilize an existing fireplace that is a heat drag on the house. In my case because I didn't have a masonary fireplace I was able to design around the stove and build the zero clearance system to help me to reduce those limitations.
Yes it is still more expensive but here is the one feature that overrides all others. THE WIFE IS HAPPY. She likes the looks. she likes the heat. Even though I could have perhaps spent 1/2 as much on the install of a free standing unit and gotten the same heat, she only liked one of the free standing units it was one of those modern looking jobs.
In the end because of how it is "Built in" we added $10 K to the value of the house (based on the appraisal) for $4 K in materials and my work.
A stand alone unit wouldn't do that.