That has less to do with it being hard to craft bribery laws and more to do with the fact that the current bribery laws are entirely ineffectual. It's absolutely something that could be fixed, but certainly not something almost any politician would want to fix.
I will grant that companies would lobby hard against an anti-advertising bill (which means it'll likely never pass). That doesn't mean you couldn't make one that's pretty effective.
But, again, the nature of advertising makes it quite easy to outlaw. Unlike bribery, where a congress person can shove gold bars into their suit jackets in secret, advertising has to be seen by a lot of people to be effective. Making it something that has to be done in secret will immediately make it harder to do. The best you'll likely see is preferential placement of goods in stores or maybe some branding in a TV show.
There has probably never been a human society in history or prehistory without bribery, and no possible set of bribery laws could conceivably create one. This is a property of human nature, not the current set of laws in one country.
I think the same is probably almost true of advertising, though maybe societies without money such as Tawantinsuyu are an exception. But I don't think you can have merchants without advertising, because, like fraud, advertising is so profitable for merchants that they will do some of it despite whatever laws you have.
Just because some corruption always will exist, doesn't mean that there aren't societies which have enforced laws that are more or less effective.
This binary thinking doesn't need to happen in a policy discussion. We don't need a perfect set of laws or rules to make things better. We don't avoid having a law just because someone will violate it. For example, a speed limit is still valid to have even though most people will break it, some egregiously so. DUIs laws are useful even though people still drink and drive.
It just so happens that with advertising we can be particularly effective at curbing the worst offenders. That's because advertising is most effective when it's seen by the largest number of people. I don't really care if a company tries to skirt an anti-ad law by paying an influencer millions to wear their product, so long I'm not forced to watch 20 minutes of ads in a 20 minute video. An anti-ad law would force advertisers to be subversive which is, frankly, fine by me. Subversive ads simply can't be intrusive.
I will grant that companies would lobby hard against an anti-advertising bill (which means it'll likely never pass). That doesn't mean you couldn't make one that's pretty effective.
But, again, the nature of advertising makes it quite easy to outlaw. Unlike bribery, where a congress person can shove gold bars into their suit jackets in secret, advertising has to be seen by a lot of people to be effective. Making it something that has to be done in secret will immediately make it harder to do. The best you'll likely see is preferential placement of goods in stores or maybe some branding in a TV show.