A rather unhistorical view afew - see his objection to the Italian influenced works popular with artists and critics of his time - he died in 1840 - a few decades before Impressionism.  This would have seemed incredibly "natural" for the period and have met with the kind of criticisms the Impressionists got at the beginning. You don't have to like it of course, but it's useful to see it in context and how naturalistic it was for the period.

As it happens, there is another exhibition referred to today in artdaily.com which features exactly the kind of really constructed, Tolkien-illustration type painting popular at the time Friedrich was working. But even Hackert's works were seen as rather naturalistic for the period before Friedrich:

HAMBURG.- Jakob Philipp Hackert (1737-1807) regarded landscapes as natural events, and his precisely observed depictions of geological and atmospheric phenomena marked a turning point in 18th-century landscape painting. For the first time, a comprehensive exhibition of Hackert's work is being presented at the Hamburger Kunsthalle in cooperation with the Klassik Stiftung Weimar (Foundation of Weimar Classics).

... he spent the greater part of his life working in Italy. Here he established his reputation as an internationally acclaimed artist and contributed greatly to shaping the image of Italy before 1800. Besides veduta, harbour views and hunting scenes, Hackert above all painted atmospheric landscapes in the Roman Campagna, Tuscany and parts of Southern Italy such as Naples and Sicily.

http://www.artdaily.org/index.asp?int_sec=11&int_new=27453

Maybe it's because I'm a Londoner - that I moved to Nice.