"is ideal" is a correctly formed and usable phrase in written English. You can use it to show that something is perfect for the purpose or situation described: This house, with its open plan kitchen and living room, is ideal for family living.
Their existence is ideal.
Overnight is ideal.
This stuff is ideal.
Winter is ideal.
CYBERSPACE is ideal for spies.
A foot is ideal.
Baseball is ideal for children.
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com