FYI:
Nov 13th, 3 years ago , BTC was ~$1275 per coin, it has been going down in price for years, and the people that brought at the high, all lost money on BTC.
For my information? I know, I was watching at the time as it flashed new ATH in the corner of bitcoinity!
It hasn't exactly been going down for years, it is lower than it was for about 4-5 months in late 2013/early 2014. That was a bubble though.
The problem with bubbles is, you can only really see them after they have popped. It is harder again with Alts as they are hundreds of smaller markets that each fluctuate.
The Combined Altcoin Market Capitalization chart doesn't look very bubbly (I hadn't seen that chart until today), it does look like it is at a quite high level though. The Bitcoin dominance is lower than historically too, even though the price of Bitcoin is historically high. I guess we will find out soon enough!