Unfortunately, that means that you’re taking a vote away from the candidate from the two main parties that is closest to your views, which helps the candidate you oppose the most.
The two party system is truly problematic, but when it comes to November you have two options currently and voting for a 3rd party has the same impact as not voting at all. Voting for the candidate that you oppose the least lets you put a finger on the scale to at least try to avoid the worst possible outcome relative to your beliefs and values.
I understand your viewpoint, but don’t subscribe. Voting isn’t about supporting a system. The system exists, with or without your participation. Shy of a full blown civil war (which is more likely to make this worse than better), the only way to change the system is to use the system to change itself. The general election in November every 4 years is the last stage of a long process that starts with local parties and elections, weaves through the primary process, and culminates on election day. We need more people that are dissatisfied with the candidates to get more involved, not less, and to go to the early phases where a smaller number of active participants can have an outsized impact on the whole system. To me, one of the many alternative voting systems would be a huge improvement (I have preferences, but honestly just about every one of them is better than the First Past the Post system we use), so advocating for that and supporting local candidates that can push those ideas forward is where my energies go.
Both parties actively try to give voters from the other party reasons to be dissatisfied and disengaged. Don’t play into it.
Also
People might if any of the third parties had a serious candidate and a serious governing platform. Each of them is fundamentally flawed in one way or another, and a few of them are flawed from top to bottom. I get that you’re dissatisfied with the status quo, but which one of these 3rd parties would be able to actually govern and not make a complete and utter mess of everything? Could you imagine if one of the major 3rd parties actually won? It would be an unmitigated disaster.