It verifies enough information to be secure. It is obvious that at one point they need to connect to some node because this ia the way blockcgain works.

Ok sure, connect to another node. But a light client is its own node.

That doesn't exist per definition. You cannot have a light client that its own node and it is not the node defined in the specific blockchain. The bitcoin innovation was about using a common ledger for every node and the nodes must run specific code to check that the blockchain state is the correct one.

If you find a way a node can do less work that what is doing now without relying on another node you would discover something new at the computer science level, so this light node will transform into the definition of a node.

SPV client security is enough for numerous use cases and many call them "light clients".