In sum, a man could get his degree at Oxbridge in the 18th century along with an education or not,..(snip)to pursue their intellectual interests. Where else could they go?

He could go into the Army, The Navy, Public Affairs, The East India Company, Trade, and Politics, all but the last of which had their own systems of training, and all of which did not necessitate a university education.

The Army required purchase and a private income and was notorious for its lack of intellectual atmosphere, not to say outright stupidity. The Navy was a closed, specialized, highly technical world that one entered in one's early teens. Trade was not genteel and, unless and until one had made one's pile, lacked leisure for study. The EIC was an option -- there were Company men in the 18th century who used their leisure to study Sanskrit, for example -- but it was also trade (of the most predatory kind) and required years of exile. Politics and public affairs were for the rich and for a few talented outsiders like the elder Pitt and Burke who could obtain upper class patronage. The Church offered gentility, a secure although no means opulent income, and abundant leisure. If a man of intellectual interests without a private income wanted to study and perhaps write on economics (Malthus), geology (Buckland), antiquities (too numerous to mention) or the classics (likewise), a C of E living offered him a safe, comfortable and respectable place to do it.