Hasn't been true since July: https://blockchain.info/charts/avg-block-size
> full blocks and high fees have caused Bitcoin to lose many users to alts (LTC, ETH, ETC, DASH...)
What's the evidence for this? All my friends own btc and alts... but none of them transact in it. They own them only for investment purposes. I don't think anybody is using alts for their higher throughput.
Yes it's true. I said WEIGHT not SIZE. A distinction few understand. Check the kWU column at https://blockchain.info If a full node has built a 4Mweight/1MB block, it is full, because non-segwit txs have wasted the 4M weight quota and prevented the block from growing over 1MB. If segwit adoption stays low, blocks WON'T be able to grow much beyond 1MB.
In fact the problem is that the rate of adoption of segwit is too low compared to the rate of increased txs that Bitcoin needs to be able to support. Therefore blocks are going to continue to stay at or near the ~4M weight quota.
The tx rate of ETH, LTC, and other alts started sharply increasing in March/April 2017, which is exactly when Bitcoin blocks reached capacity (~250k tx/day)
7% in two months. What kind of adoption had you expected? Everyone won't switch over night, that's the whole problem behind why flag dates in distributed systems are hard, and why many people adocate backwards compatible changes whenever possible.
> if Core simply agreed to double the block size
Core is the name of the Bitcoin software. Perhaps you mean the Bitcoin community? The functionality needed to roughly double the block size was released last year and finally took effect in August. If that's too slow for your use case, then you are probably on the edge of where Bitcoin is useful anyway. It's hard to imagine any sort non-contentious hard fork planned and executed in less time than that, without endangering other people's money.
None of this is very relevant to the uptake of segwit transactions however, unless as a what-if scenario had segwit been done as a hard fork instead. That was the original intent of the proposal, if I remember correctly, and there was a lot of discussion at the mailing list exactly how this should best be deployed. Looking back at it, it is quite clear it could have been deployed quicker had another mechanism been chosen.
I think you fail to envision how the dynamics will play out if Segwit2x wins. Core will simply merge the ~1k lines of code that make up the segwit2x features, and mostly everyone will be back to business running Bitcoin Core instead of BTC1, since the two code bases would be equivalent. That's it. No big war. No mass resignation of Core devs. No ceding the control of Bitcoin to "another group". Most Segwit2x supporters want a smooth "reintegration" scenario like that to take place. We don't want to "fire Core" or such nonsense you might read on r/Bitcoin.
Things would be a lot simpler if Core simply agreed to double the block size. That's all we want. A one-time block size increase, to give the blockchain some breathing room while we all continue to work on off-chain scaling (NimbleWimble, LN...) that we all already agree are the proper long-term solutions.