The Lightning Network may take an even longer time.
I doubt that we'll be seeing the full effects of the Lightning Network until a year or two from now, and by then this bull market is fairly likely to have subsided.
Hopefully the Lightning Network will develop well with a more peaceful environment and a more stable price, so that it can be used well by merchants later.
Well, there are still people who believe that everything should be verified on chain. That's really all that's holding Segwit back at this point. It's ready for adoption. Resistance is so strong that Bitcoin Cash was born, and it's actually gaining and maintaining its ground.
Segwit does verify everything on chain. Pre-Segwit nodes don't verify witness data, but they do verify Segwit transactions against the consensus rules and they are able to process them. Lightning will bring lots of transactions off-chain, which is actually great for privacy. It's a different trust model, sure, but the technology is sound. I just wouldn't keep more than 1 BTC locked into channels.... and I would consider that a very long term spending wallet.
Regarding slow adoption, I think it's more so a political stance that some companies are taking because they want massive scale now and they want capacity upgrades as needed. Mike Belshe (BitGo) comes to mind. They don't want to wait years for robust Layer 2 systems to come to fruition. I'm guessing that there is also pressure from shareholders who value company growth above the good of Bitcoin.
The Bitcoin Cash price is in a death spiral vs. Bitcoin, and it's really just backed by a few big players like Roger Ver and Jihan Wu. It managed to co-opt most of the Bitcoin Unlimited camp, but that was a pretty small community already.