You show clearly you don't understand what the mental load actually is.
60% is rarely good enough simply because you felt it was doesn't mean. It is so.
You say you go on amazon and get what they want. That suggests your children are still quite young?
What about the teenager that is into specific Japanese fashion that takes 2-3 months to arrive?
The teenager who wishes tickets for a show/match that goes in sale in September?
The kid that doesnt want anything much as they are going throufh a bad mental stage?
The parent you love dearly that has everything?
The family member that lives abroad so you need to order 2 months before their significant day (tnx Brexit)
None of those can be done on Amazon... most take more than 5 mins too. They require thought and planning.
What about the teenager that is going through their first heartbreak and needs supporting?
The 3 teens whom all has a rugby match in 3 different places on the same day?
The child that's being bullied at school and isn't coping needs additional support?
The dyslexic child that's not being supported at school?
The autistic child who you can't get a EHC plan for?
The child who is suicidal so needs 24 hours watching but you can't get outside support in.
The child with a kidney issue where school keeps calling you as their attendance is low while they are under GOSH for their kidney issue (that was my son btw and school was the one who regular sent him home as he was very sick)
The child whose parent died suddenly who needs more support than before the person was your x and you parted on negative terms.
The parent that starts to suffer from dementia and you need to source support for meanwhile
You pick up the slack.
To me a takeaway a week is not "the occasional" its a regular thing. Also your original post suggested it was more than once a week.
In-between wife coming home from abroad what happened? Did you do a huge clean up before she arrived back? Did she do loads of cleaning while she was home?
While I agree the house doesn't have to be 99% clean and washing doesn't have to be done the same day. To me the house needs to be more than 60% clean and to me the washing needs to be done over the week.
The suggestions above have all been experienced by myself or close friends as we brought our children up btw. I also will bet as your children get older this will all be stuff happening in your children's close circle.