First of all, setting aside a few people at central banks and finance ministries, there is no such thing as an ‘economist.’
Nobody employs ‘economists.’ Not in the private sector, any way.
Not at investment banks, not at commercial banks, not at airlines. Nowhere. Ever.
To be sure, there are professors of economics, but they know as much about how economies function as criminology professors know about being a successful criminal.
When people really understand the economy (or some sector thereof), it is based almost entirely on personal experience (with the qualification that they often process that experience with the help of a lot of background reading and, in rare cases, a smidgen of formal economic training). And those people are usually not described as (and do not self-describe as) ‘economists.’
In terms of what officially passes for ‘economics’, it has startlingly little predictive or (so it follows) explanatory power. There is the odd economics professor who seems to catch a glimmer of the relevant facts, but he is just one voice out of many.
And even if he is right, so what? What can an ‘economist’ do? He’s not like a surgeon who can sew somebody’s arm back on or a mechanic who can replace a defective part. Exactly how is someone with economic knowledge to deploy that knowledge? Any relevant regulatory or legislative decisions will be based on the usual political and monetary pressures.
But for what it’s worth—no, I don’t think they grasp how useless their discipline is, because they’d stop practicing it if they did.