I feel sorry for my little Grandson

Goodness I so understand your perspective.
I'm sure you realise, but for your sake I feel obliged to point out, there is very little you can do about this.
You risk the parents wrath if you stand up (as they see it) for your gs against their choices.
Which could result in you not seeing him at all.
Been there done that.
Do you get the opportunity to see hom away from his home?
Can messy play be enjoyed by you both at your house or the park maybe?

See him

Perhaps, when lockdown is over (fingers crossed but not holding my breath), your grandson can play messily at your home.

I don't think there's much you can do about things in your daughter's home unless you seriously think he is ill-treated.

I wouldn't say anything or you may find access to your grandson restricted in the future.

When he is at your house, he can do what he wants . Their house, their rules. Have him over at your place as often as you can, so he can have some fun time. Lockdown will soon be over ......

The thing is crazyH ... it doesnt always work that way.
Some parents insist on their rules where ever,what ever, when ever.

Still, may not be that way for fuseta and her family

Oh yes let him be as messy dirty and wet as he wants when he’s with you keep the water bombs for your house and his memories will always be the fun he had with you

It’s a real shame because he’s going to grow to have his parents ocd with cleanliness and tidiness but occasionally people do the exact opposite so maybe he ll grow up to be an untidy mucky Long haired teenager with a degree in woodland studies or how to naturally compost the world ?

Sounds like the way to go crazyH don't fall out with your family over this fuseta or your grandson won't have anywhere to relax and enjoy himself.

Agree bluebell but I feel for him under that degree of oppressive control.

Heartbreaking

DD used to be quite obsessive over the state of their kitchen floor - not as compulsive as OP’s family, but it was always immaculate, despite the best efforts of her 3 children.
Then they got a puppy.......
?

Little you can do; he will gradually be terrified of making a mess of any description anywhere; exactly like my ex sister in law and her son. She spanked him with a hairbrush because he spilt washing powder over the kitchen floor. (Long time ago.)
I shuddered when I saw a magazine feature on a beautiful house furnished almost entirely in white; 'my sons have grown up in a white environment ever since they were born and they are trained not to make a mess', said the beautifully pristine chatelaine, grimly.

My 2 step daughters grew up with a mother like this and both went completely the other way.

An adorable puppy brought her to heel Maw?
I think its perfectly natural to get a bit finicky about keeping the house tiptop. I'm sure we all do for a while.
Seems important doesnt it, at the time?
You ok?

Well she is still fussy, but has more important things to get stressed about than a few crumbs ?

Sounds awful eazybee

I’m fine Namsnanny - but do wonder sometimes how I brought up three DD’s to have higher standards than their mum!

Have a different régime at your house and get a dog.

I think that when children grow up like this, they end up living in a pigsty when older. Could you ask one of her friends or a relative who she is close to to talk to her? Or does her MIL feel the same as you? If she does, could you and her talk to your daughter and SIL together? X

I have one DDIL who is incredibly tidy. Every garment in every drawer is neatly folded. Toys are tidied away non stop. The other is complete opposite..... love them both but am far more at ease in the latter !

Is there any chance that at some quiet time you could sit down just with your DD and have a calm discussion about this? I think it’s really harmful behaviour with potential long term consequences for the poor child. There’s a very big line between temporary easily cleaned up mess and mess or damage that takes ages to put right.

Next time he is at your house you can give him the opportunity to let his hair down and get really really messy!

What a shame for this little lad - there is nothing you can do at their place without rendering yourself an unwelcome guest.

Could you have a pet at your home? Even a goldfish as you mentioned but you could have stick insects. If really brave a couple of rabbits ? Your house your rules. Keep a few old clothes at yours so he can get dirty doing a bit of gardening such as filling pots etc. A watering can from Poundland keeps my 4 GC busy for hours. Drown the plants mind you as they always seem to water one particular pot !

Well, at least your DD's home will be much more Covid free than mine!

Oh I love mess. And I love making mess with DGD