Depth and volatility are correlated most of the time. As volatility increases depth tends to go down and vice versa. Roughly if the ES range is average 40pts per day, i would expect approx half the depth as when the range is 20pts per day (all other things being equal). This is because limit orders are spread out more as prices are expected to reach wider extremes on every move that occurs.
Use it or lose it...it won't last long but things may last a little longer due to the pending U.S. elections. Also, I've traded in 1999. Like you, I do not agree that market conditions (the context) are the same for so many different reasons. We'll just need to wait and see if price reacts the same especially with the pending U.S. elections.
It seems the market is going to grind higher until the next US recession or the next nasty black swan event. I wouldn't get my hopes up regarding sustained volatility before then but we will continue to get short term bursts of volatility every know and then which can be traded if you have good discipline.
Looks like VIX is getting momentum. Could very well see another month and a half long volatility roller coaster.