I've actually used several newer Echo saws, since two of my cutting partners buy a lot of Echo, but they're all heavy and underpowered when compared to the better models of the big two brands (Husq/Stihl). The last Echo I personally owned was indeed older (510EVL), for the simple reason that they haven't made anything that keeps up with the other brands on power/weight ratio, in the three-plus decades since.
Look at the brand new CS-590 the OP posted. It's only 0.50 kW/kg! My 30+ year old antique Stihl 064 AV is 36% higher at 0.68 kW/kg. My similarly old 036 PRO is 0.62 kW/kg. Echo has always lagged behind, but when their newest saws are coming in 30% - 40% lower than antiques from Stihl and Husqvarna, you can understand why people who are really into saws are just not buying them.
Echo makes a good market on cost and reliability. They're reliable, and less expensive than pro saws from either Stihl or Husqvarna, which is a good combination. They all have their place, different strokes for different folks.