I used to go with packed lunches, but you still have to pay for a locker to store them or cart them around half a day. And eating a full bento in a queue is something I just can’t do, it’s just not the done thing. An onigiri is OK, but a full meal... perhaps on a mat waiting for a parade. Thing is, you aren’t supposed to bring meals in, even though snacks are tolerated. There’s a picnic area next to lockers just outside both parks set aside for exactly this.
Anyway, after bringing in home made and store bought bento over several years we realised that the food in the parks wasn’t much more expensive and, with some exceptions (Woody’s Horseshoe Roundup is one ) the food is decent and enjoyable. And if you can avoid the 12am-1:30pm scrum, queues are manageable too - at least they are in mid April.
I’m as penny pinching as they come (I’m sure I have a reputation on this forum for appreciating value for money) but I don’t take obento to Tokyo Disney anymore. And this is coming from someone who will use a vintage popcorn bucket and make popcorn that very morning and take a refill pack with us AND who saves the monorail fares by walking to and from Maihama Station and Disney Sea. As I said - PROPER penny pincher!

EDIT TI ADD Here’s the official line about not taking food in:
https://www.tokyodisneyresort.jp/en/...ce/detail/013/
An exception not mentioned is those with dietary restrictions. In cases where visitors can’t expect to have their eating requirements catered to (religious/moral/allergy etc.) they can take in a lunch box and have it heated at one of several restaurants and cafes in the park, they’ll be expected to eat it there too.

I thought my own kid was too young at 2 and a half when her grandfather took her to Tokyo Disneyland. Boy was I wrong. We arrived at opening and she stayed awake right until the last firework went off. Then she was out like a light.