、、。
Forty percent of the workforce are white-collar workers, and the majority of them do boring, ridiculous make-work jobs.
Literal
Labor-force [genitive-の] 40 percent [topic-は] white-collar workers [being-であり], their [genitive-の] majority [topic-は], boring-and silly made-up work [object-を] are-doing.
Polemical essay writing. ~であり chains the first clause into the second with the formal conjunctive copula, a hallmark of essayistic register. 退屈でばかばかしい stacks two adjectives with the で-connective: 退屈 (な-adjective, 'boring') + ばかばかしい (い-adjective, 'ridiculous, absurd'). ばかばかしい is the reduplicated intensive form of ばかしい, carrying stronger contempt than just 'silly.' デッチアゲ is the colloquial noun form of でっち上げる ('to fabricate, concoct'), often written in katakana for visual emphasis — 'made-up,' 'trumped-up,' 'bullshit' in the pejorative register. デッチアゲ仕事 = 'bullshit work,' 'made-up jobs that don't need doing' — a direct jab at pointless corporate roles.