So what? Parties have the right to choose their candidates by their own rules.
Our primary system is totally screwed up anyway. The presumptive Republican nominee and the Democratic former-underdog turned almost-frontrunner both owe their status to independents (and maybe crossovers for the Republican) voting for them in states that have open primaries.
As to the candidates themselves, no comment, but both parties maybe saddled with candidates chosen for them, at least in part, by non-party members.
Nominees should be chosen by parties, not “the people”. I’d have no problem with ditching primaries altogether and going back to having candidates chosen by bosses in smoke-filled (well, probably not anymore) rooms. It’s not like there has been a big improvement since we “democratised” the selection process with primaries and caucuses.