Maybe your understanding of lightning is wrong here. Yes you open channels, and transactions in lightning need open channels, but you do NOT NEED to open channels for specific transactions. You open channels once, and transact over them for years. I run a lightning node with more than 15 channels (each to different lightning nodes) that are all older than 1 year (I route payments, so I have way more channels than needed). You can batch-open channels, i.e. I could have opened all my 15 channels with a single on-chain transaction. Taproot update would make those "commitment transactions" onchain way smaller (in byte) than needed to in the past.
Once channels are open, the users on the lightning network can transact back and forth without any new channel opens/closure and thus no on-chain settlement. Hence: Throughput in lightning is not at all limited on the bitcoin transaction throughput.
