Segwit needs 95% approval from miners(never going to happen) and only solves blocksize issues short term.
Segwit solves it long term because it enables for proper Lightning Network usage, which is the only way to scale to mainstream levels.
Lightning would take at-least 4-5 years to get activated. Also, it's an off-chain solution not on-chain solution which Satoshi advocated for. This means value spilling over from BTC into other more transact-able alternative currencies.
Remember SegWit is the on-chain solution. The SegWit activate is the important thing to implement Lightning Network. Although we can still run LN without SegWit but looks like if that will not help a lot.
SegWit for the bitcoin malleability fixed with a lot of benefits.