Agreed, but I wouldn't get bogged down in quantity of altcoins, the only relevance is the market cap or dominance of these altcoins, whether there are 100, 1,000 or 1,000,000.
For example BTC dominance was at a monopolizing 96% at the bubble top of 2013, then during the bear market dropped to 94% followed by 92% and continued to decline from there.
It's recent peak in 2017 was at 67% (after dropping below 40%), and this month has re-reached 58% after falling to an all-time low of 32% in Janaury. Long-term dominance is still falling, until there is evidence to prove otherwise, this BTC gain in dominance is nothing more than a dead cat bounce after falling from above 90% at the start of 2017. Bear market or not.
If history repeats itself, then the dominance won't be able to climb above it's December 2017 high, in the same way in 2013 the dominance didn't reach new highs during the bear market either, because the overvalued altcoin market had already become oversold. Hence the reversal was a little earlier than BTC that needed more time to consolidate.
If you're not seeing some peer-to-peer currencies outperforming BTC since August then check them out; XMR, NANO and most recently XRP.
I've been waiting a long time for a consensus on altcoin bearish sentiment, this is a key indicator for me personally.
(Observe the masses and do the opposite)