I sometimes wonder how feasible is it to completely avoid loanwords, i.e. 漢語 and 外来語, but still using Modern Japanese (i.e. not simply just using Old/Classical Japanese vocabulary). Is the 和語 inventory of Modern Japanese still intact enough to express arbitrary ideas, or at least enough to write article-length things? I suppose some workarounds would be needed (say, 日本語 as ひのもとことば?) but would it be technically possible, or has enough supplanting happened that some concepts are just impossible to express without loanwords?
I think the answer is "yes, it's possible...but you'd be inventing a whole other language." To be able to describe modern concepts in an old language, you'd still have to invent new words, and if you restrict yourself to only using 和語、it's not going to be comprehensible to Japanese people.
Such an experiment is happening right across the sea, in Korea. While South Korea has occasional use of Hanja (that is, Kanji) and beaucoup loanwords, North Korea has taken a firm stance forbidding Hanja, and discouraging usage of loanwords.
As quoted here: "South Koreans puzzle over what North Koreans mean by a "vehicle that goes straight up after takeoff," when the simple English word "helicopter" will do."