There isn't any problems with a sustainable block size increase.
But, isn't it a temporary solution? What will happen once that increase isn't enough to cover the same security it did before a certain halving in the future? Unless we double the block size each halving and the miners always fill their blocks with others' transactions we retain the same security given that the price remains the same.
But none of the above will ever happen. There will always be empty or emptier blocks; there'll always be fluctuations in the market value.
Answering both:
There is no such thing as decentralization when it has always been far better for an average Bitcoin user to be running an SPV client instead of a full node.
Half of the network is probably now secured by $10k a piece machines that would blow the circuits in a lot of houses when plugged in yet we're facing a threat of centralization because of the $200 2tb ssd. Really?
Aren't we using a system where each user can verify by their own the validity? Sure, few pools control most of the computational power that is offered to the network, but the average person should always have the right to verify what they're receiving. If you make it too expensive, there's discouragement.