Too much isn't a problem, if by that you mean it would be too empty. For most of Bitcoin's life the blocksize has been too much. Was never a problem. Most altcoins that claim high tx/sec have large almost entirely unused blocks, not a problem for them.
too much is also a problem, it is not as serious as too little but still is. if the blocks were mostly empty then it becomes easier to spam the network with more junk and cause problems. remember that spam is not just increasing fees, it has different forms. for example one form is to increase the number of UTXOs and make it extremely hard for nodes to run since they would have to load up a much bigger UTXO database in memory and look things up.
you can't compare bitcoin with altcoins either. because there is no incentive to spam attack an altcoin but there are lots of incentives from all sides to spam bitcoin!
i agree with the rest.
The way I see it, LN opens up new possibilities, like everyday $5, $10, $50 transactions, or even microtransactions. These are things that aren't really done currently on bitcoin, as the blocks are currently mostly filled with people just moving money between wallets or exchanges. So the LN does nothing to solve the current problem,
actually one of the most important usages of LN is when people want to make lots of transactions like when they move their money between their wallets and exchanges. we only need one exchange to start an LN node and traders to move their transactions there to see a decreased number of on-chain transactions. there are a lot of other cases too, like gambling sites and mixers.