From my poor understanding, their fork theory try to resolve 3 issues.

1. Scalability:
I saw different solutions on this issue. If all business run on one chain, it has huge pressure on performance. And the nodes dont need all ledger but the ledger they cared about. From this perspective, it is good to have different block chain to support different business, and communicate with each other with careful authorization and trust (consensus).  
I am NOT technical expert, while I heard different solutions. For instance, EOS and previous graphene from BTS could support really high transaction rate. And Vitalik also emphasized the performance issue is going to be resolved in next 2 years by "sharding" at DEVCON summit.
Also Lisk has side chain which try to make Dapp development as easy as possible at the same time. The side chain technology can partially resolve scalability issue ,if I understand the tech correctly, and kind of isolate security issue.
Ok. I missed the lighting network on bitcoin network and ethereum, the off-chain technology is suitable for low fee, quick, small payment, and also cross chain atomic exchange.
What's the advantage, difference, and the current progress of the each technology?

2. User base:
The recent Bitcoin fork show lots of debates. Some radical users support one of them, and look down upon others. While lots of BTC holders don't care the debates and only care the "free" coins. Should I say you can get free users from fork? I don't know, probably people just care free coins. The technology behind represent the core value. You need people support the core value, which need "real" innovation based on current chain.  At this point, it related my next topic: do you think people who know very little about blockchain should fork any chain?

3. The barriers building one's own blockchain.
We have to admit it is still the early stage of blockchain technology. I dont judge on various blockchain solutions, and they are valuable innovations.  The market may finally determine the winner, maybe it is the one what you think it is impossible. So I support more and more people enter this industry, learn, contribute, and evolve continuously.  
I do think as a Dapp developer, he need understand the basic knowledge of blockchain, but no need to know the tech details of blockchain. For instance, he should never change the consensus, encryption, which should be done very carefully. However he could build the Dapp using his current skills on normal internet Apps.  The blockchain cornerstone guarantee App transform into Dapp. So I think they are good attempts, like ethereum using solidity, even it is still vulnerable, and like NEO using multiple programming languages, and like Lisk which helps to build Dapp. We need avoid the issues on parity's multi signature, but don't stop try, what makes the technology improve.
Building one's own blockchain is similar with building Dapp? I am doubting. I am not saying we only need one blockchain in the world which could resolve all issues, but is it really good that every one build a blockchain easily? It's hard to differentiate scammer and real builder. And Achain has the rule to approve the fork. It doesn't describe the detailed rules, at this time I keep my neutral opinion.