Let me start by saying that I think this will split people and some might agree but I think enough on here disagree that it qualifies for this community. I should also give a caveat that I’m not 100% sure all of this applies to the GOP structure, so I’m using the Dems as an example.

People often think that, since the two major parties in US politics don’t perfectly reflect their views, they shouldn’t waste time getting involved in politics. But who picks political candidates and platforms? The DNC picks nationwide candidates but endorsements are typically done at state and local levels. Local committeepeople who set local agendas and endorse candidates are just random people like you and me (state ones are slightly higher profile). If you want to shift a party in a different direction, join it and be part of the change. Most of the time, the committeepeople run unopposed at the local level and with minor opposition at the state level. Endorsements are powerful and hinge on an even smaller number of votes than local elections. And even within the local committees, there will often be a small-ish vetting committee that recommends endorsements to the full committee. Especially in primaries, a lot of people just vote for the endorsed candidates.

You might be thinking “but there’s a third party that better matches my views, should I join them instead?” I would say no in most situations. The political reality is that we have a 2 party system with first past the post voting that ensures those 2 parties stay in power. Even if, for example, the Green party won a decent chunk of house seats, they’d have to form a coalition with the Democrats to get a speaker in power that supports their mutual views and a middle-ground agenda.

Tl;dr: if you’re worried about a political party not matching your views 100%, join it and change the party.