SegWit is associated with Bitcoin and its core principles, so its strengths and weaknesses will vary depending on who is observing it.
SegWit’s ability to give blocks more weight, or transaction density, relies on the idea that some blockchain data will be kept off the original chain, which is instead used as a sort of reference or index. Some believe that offloading data from the blockchain is already a failure, as it’s like admitting that blockchain alone can’t function.
From this perspective, SegWit itself is a weakness infecting Bitcoin, and that’s why rather than implement SegWit, a piece of the community hard forked into a new blockchain called Bitcoin Cash in 2017.
Bitcoin Cash is essentially legacy Bitcoin before SegWit, and its scaling strategy is simply to increase the block size and keep all data on-chain. This is a decentralization strategy opposite that of the Bitcoin Core group, which sees SegWit as the first stack atop a multilayered blockchain.
There are countless more ideas that riff off Bitcoin or Bitcoin Cash, or take a new tack. SegWit is simply one step in what the largest developer group of the largest cryptocurrency believes is the right path.