My main gripe with them is that they mix flavours so LO doesn't really know what chicken actually tastes like as its chicken and something else. Same with fruit, its got other things mixed in with it. And as jars have added water etc to them the texture and so on is different. Also so is the flavour. No matter how good the puree it doesn't taste as good as home made IMHO. Also the colours are never the same as when you make home made purees. Children don't learn how to recognise foods they like or colours of foods etc as its all mushed in together. And then when moving on to solids it can make the transition difficult as they have to then adjust to flavours of foods not mixed together and don't recognise them. Babies won't be used to home cooked food and will be used to flavours from jars and real food doesn't taste like that.
Making your own ensures that unless you choose to mix flavours your LO will taste each food and develop tastes for the foods rather than mixes of foods. When I used to make purees for babies I was looking after I'd make seperate purees and not mix them before LO's ate them. For example I'd make broccoli puree and then a chicken one. And baby would have two flavours separate, not mixed together. Made sure LO's knew what food was what and how it all tasted. I'd put only one food on the spoon at a time. As they got older and moved on to new foods we'd do the same. And then onto solids the same way. .
If someone served me up a pile of goo and said 'yum chicken casserole with carrot and potato' I'd not eat it. I'd want to experience all the flavours apart and then have them mix in my mouth as I chewed (if I put more than one food on my fork) or apart and have a different taste from the place with each new food. So I'd not give my baby jarred puree based on that. Honestly, if I sat down and ate a jar of puree with my baby I'd think it was gross. And if I won't eat it, why should he. One of the main reasons I don't give my LO mixed purees (he has stewed apple only) or jarred food. Yes it might be a pain to go the home made route but I guess it depends on how strongly you feel about things. For me personally I wanted Galen to eat what we eat and to not feed him purees or wean before 6 months (ish). Hence doing things the way we have done. What works for one isn't for another, so each to their own