Sidechains are not a workaround, even ignoring that they're centralized and marketed as such.
Sidechains only solve the problem of user scalability, not volume scalability, because they still require the Bitcoin network to verify.
For example, on a side chain it would take seconds to make 10,000,000 transactions between 2 people, but making 2 transactions between 10,000,000 people would take over a month.
It's basically a network of "payment channels" you can route instantaneous off-chain payments over, which occasionally settle on the blockchain. And you don't need to trust anyone in the network with your funds.
Sidechains only solve the problem of user scalability, not volume scalability, because they still require the Bitcoin network to verify.
For example, on a side chain it would take seconds to make 10,000,000 transactions between 2 people, but making 2 transactions between 10,000,000 people would take over a month.