I've been in this space since 2014. I have always been a Bitcoin Maximalist. Than 2017 happened, and it was hard not to chase altcoins. After the hype died down, and the dust settled, I realized that there is room to be a BITCOIN/ETHEREUM Maximalist. Every other project is a "me too," or a clone, or redundant, or vaporware. The only two blockchains we need right now are Bitcoin and Ethereum...and we need BOTH! Not just Bitcoin anymore.
I love Bitcoin...LOVE it! But when it really comes down to it, I use Ethereum in actual, practical use cases. I recently bought something in USDC...which utilizes Ethereum. Stablescoins, ICOs, IEOs, SEOs, Defi will be built on Ethereum.
I have fallen in love with Ethereum as hard as Bitcoin, and I see value in both. Ethereum is extremely elegant, and may end up being more important in this space than Bitcoin one day. It is the foundation of the Defi movement.
So there can be a category of people who consider themselves BTC/ETH Maximalists.
Right now, they maybe top 1 and 2 in the rankings but it doesn't mean that they are the king as the demand will always depend to it's uses and whether the demand is being accepted by the government or not. Every hurdles will affect the demand of any coins like btc, eth and other top coins/tokens.
I also consider both as the most important coins right now but due to high transaction fees in btc, I tried other coins as alternative to send a small amounts. I always see things fairly and I cannot devote myself to btc and ethereum only so I cannot say that I am a btc/eth maximalist.