As hammerzeit mentioned, a lot of bullshit jobs are there because of an arms race. Your competitors have marketers, lobbyists and corporate lawyers, so you need them too. If everybody fired 90% of their marketers, marketing dollars would go 10x as far, and things wouldn't change much.
Just take a look at marketing. It's an industry that's so big it props up newspapers, television, Google and most of the rest the web just as a side effect. You can argue that's a good side effect, but there are plenty of bad side effects like the invasion of privacy, cluttering up urban spaces, breaking up TV shows, et cetera.
This is really a case where I believe that governments should heavily tax the externalities. What would happen if taxes made advertising and other forms of marketing 10x more expensive?
Advertising would become much less common, but it would be much more effective due to its rarity, so that would approximately balance out. A bunch of bullshit jobs would be lost, but the government would have a bunch more money to hire people for non-bullshit jobs like building & staffing schools and hospitals, as well as reducing harmful taxes like income & sales taxes which also increases the number of jobs.
Google, the web, TV and newspapers would lose much of their income and would have to accelerate their shift towards alternative business models, but I would argue that isn't necessarily a bad thing. Reduced taxes would mean there is more money around for consumers to pay for entertainment.
Bad side effects like privacy invasion would be reduced.
Obviously it's not all good, perhaps there are better ways of reducing this arms race.