Big blocks are similar to the tendency americans have to throw random piles of money at problems and hope they go away.
Bitcoin Unlimited: "Let's make blocks bigger and hope all of bitcoin's problems disappear."
That's not a good policy. We can do better.
Core refusing to provide bigger blocks IS the problem.
For current problems, they need to give a larger number of blocks. However, larger blocks meant security risks, which made the core worry. However, segwit can completely solve the problem. But I do not know why they reject segwit.