Parties are coalitions
Being in the majority matters.
No political party will ever match your values perfectly, because they need to appeal to a wide range of voters to win in diverse districts. Representatives with safe seats often need to cooperate with moderates in swing districts to get a majority.
In the words of political scientists Gary Miller and Norman Schofield, who studied all the elections in the 20th century:
"Successful American parties must be coalitions of enemies. A party gets to be a majority party by forming fragile ties across wide and deep differences in one dimension or the other."
You could see this in action in 2016:
"The Republicans' national success — the presidency, majorities in the House and Senate, unified control of 25 state governments — is a tribute to their ability to hold their coalition together. Many different people vote Republican for many different reasons."
No single politician can advance their agenda without a coalition behind them. Even if you don't like the specific candidate in your area, remember that politicians you do like may depend on the votes of your local candidates to get significant legislation passed.
Nancy Pelosi and Alexandria Ocasio Cortez may not always agree, but they both contribute to Democratic control of the House. Susan Collins is a relatively moderate Republican, but she helped to put Brett Kavanaugh on the Supreme Court and she keeps Mitch McConnell in power. Joe Manchin is a relatively conservative Democrat, but voted to remove Donald Trump from office. Every single Democrat voted in favor of removing Donald Trump from office. Every single Republican except for two opposed even hearing witnesses.
Example: the Affordable Care Act
The following two short videos show the way coalitions worked when it came time to pass the Affordable Care Act—Democrats had to sway wary supporters with specific home-state benefits: