There is no such thing as a perfect candidate. But there have been many R candidates who were so flawed that they lost - and never because they were “too” conservative; it was invariably because they were to middle of the road/moderate/compromising principles to get along. Or had few conservative principles anyway.
Yes, as a practical matter, I happen to think you are right. We need good, conservative candidates if we are to really have a hope of winning in the general election. And there are candidates in primaries which would be hard pressed to convince me to vote for them, and some are even too far out for me to ever consider. However, coming to a decision about which is better is often not a very black and white decision and does at times come down to a subjective process. I understand that, and so I am not too terribly hard on people who may act differently than I do, especially when there are reasons which commend their decision. I am not dogmatic about this, of course, but it is just my own personal approach.