Why are the kits so bad?

TL;DR - planning on getting a beardie in a few months; keep reading online and here that the kits at pet smart etc, are no good for a starter, why exactly??

Hi everyone! I just want to start off by saying thank you for all the hard work and dedication you guys put into researching and educating others on beardies, I've spent the last 5 hours reading as much as I can and learning so so much I never knew before and more than Google could ever tell me!

Here's the deal. My 5 almost 6 year old is on the autism spectrum and mostly non verbal. She has recently become insanely interested in reptiles, specifically lizards, beardies, and snakes! She is in no way capable of taking care of an animal on her own, but her dad and I would absolutely love to bring a dragon into the family as our pet, and have her maybe be the feeding helper for now!

We are planning to surprise her with the the dragon for her birthday in August, so I wanted to start doing some research into what it's like caring for them, feeding, costs etc. When we have visited Pet Smart to look at the animals I've seen they have full kits available with the tank and all the necessities.

Or so I thought? After spending the last several hours on my couch immersed in this amazing sub, I saw a lot of you in comments saying how bad the kits are and how places shouldn't sell them, you don't recommend them etc, but I haven't been able to find a solid reasoning behind it other than you might need to upgrade things later on? From my understanding the light that comes in the kit wouldn't be strong enough(?) But can't I still get the kit that comes with the light fixtures and just change the bulb? Or just swap out a few of the items for higher quality as the beardie gets older?

Just to be clear, I'm absolutely willing to spend more money to buy everything separately, but just curious as to if it really would be more expensive buying it separately since pricing for the kits seems to be around $250-$350 here, but a tank on its own is $150-$250. Please give me all the info, and if you happen to have any articles backing up claims those would also be appreciated!! I want to make sure I do this right! Thank you all for your help in advance!!