the problem with bitcoin is that
there are no barriers to competitor ‘coins’
such as litecoin or dogecoin
Competition is a good thing, it tests the strength of the leader. You have a valid point but the displacement of Bitcoin as the market leader becomes more unlikely with each passing minute for a number of reasons.
Bitcoin enjoys the advantage of first mover. It also has the advantage of a vast decentralized network infrastructure that has taken on a life of its own and is growing at never before seen speed.
It has wide name recognition( branding) everyone who talks about cryptocurrencies talks about Bitcoin generally.
It is being accepted by merchants now and that class of users is growing exponentially as well.
I wouldn’t say Bitcoin could never be displaced but as time passes the idea appears highly remote.