I admittedly have little visibility into the scope of NSA programs, so have to resort to media for subjective evaluation of what constitutes "massive" or "domestic".

BBC called it "extensive internet and phone surveillance by American intelligence" http://www.bbc.com/news/world-us-canada-23123964

Wired described "the vast scope of the government’s domestic surveillance programs" in reference to Snowden leaks. https://www.wired.com/2014/08/edward-snowden/

EFF refers to NSA's access to "large streams of domestic and international communications" https://www.eff.org/nsa-spying/how-it-works

Assuming that journalists tend to sensationalize I'd agree to apply a grain a salt for these statements, but is there an argument suggesting NSA's operation was fairly small scale and is not indicative of their capability to build large systems?

The argument is to look at the primary documents that the journalists were working from, which shows collection that is far smaller than what the journalists claimed.