Are Merkle trees useful or just a legacy of the white paper?

The bitcoin white paper discusses using merkle trees as a method for pruning the blockchain for lightweight verification. Indexing provides a more practical method of achieving a lightweight node, and pruned nodes cannot be shared between full nodes because they introduce trust.

Each block contains a merkle root rather than a hash of the transactions list, which introduces a performance overhead when verifying blocks.

Are Merkle trees useful to Bitcoin or just a mild design inaccuracy?