Maybe he's forgotten DCs need guidance? That doesn't equate to wrapping them up in cotton wool.
Many DCs are still slow at getting themselves organised, at this age, nothing unusual. Post-Its and a list can help DS focus. Taking the consequences of being perpetually late or forgetting kit or homework might persuade DS to try harder.
Adults can set a good example. Other niggles can be addressed, eg no phones at the dinner table, coats put away, food debris and packaging cleared away after snacks.
It's nice when you can provide material treats but they're not life essentials. Pocket money is a privilege not a right. When you say you are paying for the bulk of DS's wardrobe, are these clothes designer labels or something? Otherwise seems a bit odd when you all live together and OH is DS's dad, unless all household expenses are split equally.
How do you discipline, consistently or erratically? You and OH may come from differing attitudes and backgrounds. I wonder how old his other DCs were when his relationship with their mother ended? Perhaps he has an unrealistic idea of how DCs are at 10..
Quite often when a partner comes out with this criticism it signals he is feeling neglected, rightly or wrongly. . Obviously working as a team will free up time for you both. Do you and he get any time to yourselves?