Here we go again, threads that are a result of inadequate research. 2 MB block size limit:

• Increase storage requirement (the blockchain is already huge(
• Increased network requirement
• Attack vector at 2 MB (validation that takes longer than 10 minutes)
• 2x TX capacity

Segwit gives you almost the same amount of TX capacity while avoiding the attack vector, scaling down the validation from O(n^2) to O(n) making it linear. It also comes with other benefits and fixes required for LN.