like i have to download another chain with global data in order to verify its state. but its way more bigger and faster than base layer, so i can't. lightning for example is a good scaling solution. because i don't require to know ledger state of everyone using lightning. its just a ledger between two parties that know each other (i think new lightning protocols allows more as well). if you scaling solution is just another chain with faster and more data, its not a scaling solution. i still have to download it all to verify it. or trust someone else.