True. If I was google I'd spend millions getting lawyers and lobbyists to try to change how fair use is applied and interpreted in the U.S. so it is as clear cut as "an excerpt of up to this percent size of the total work is fair use regardless of context" combined with "excerpts are not permitted to be pieced or packaged together in such a way that the entire or most of the original work can be consumed". So you wouldn't be allowed to just make a playlist of 30 second clips on youtube that equals the entire movie, but a stupid script could figure out if a clip counts as fair use.
To clarify, this would work the same way classified information works in the DoD -- many small pieces of information can be one classification level (or even unclassified), but if you aggregate them, they can become a higher classification level in aggregate. Similarly, small fair-use clips on an individual level would retain fair-use status, but if you start aggregating them, via a playlist or some other method, the playlist would not be fair use and would count as infringement.
The ballsier move than simply lobbying forever would be for Google to just go ahead and do this -- go ahead and write a script/AI that rejects infringement reports and/or DMCA requests on excerpts that are less than 5% of the total work on the basis that such a small excerpt necessarily must be fair use no matter the context because of the small size of the clip, and then battle each case out in court on behalf of the infringing user. I think they would win every single case, and once they have won a few in a row, precedent would take care of the rest and predatory media companies would stop trying.
This isn't impossible. Google is in a position to clarify / influence how copyright law is applied, and they should do it.