The purpose of the GOP is to run interference for the left to make it easier for said institutional left to administer the state, and through its administration of the state, the rest of the society. Criticizing the GOP for performing its function is confused — there’s no other role for it to play, considering its non-representation in important institutions like government bureaucracies and, more importantly, universities.
The GOP functions to contain discontent among the population, to channel it into useless issues, and to tell people what they’re allowed to believe and express without provoking social opprobrium and legal consequences.
Wanting to replace the GOP with a new party would just mean taking over its function — which is to perform as a catcher, political policeman, and misdirection apparatus for the state — really not terrible work if you can get it, but nothing like actually controlling the state or changing the methods by which it operates.
Deliberately breaking the ability of the Republican party to field national candidates is worthwhile for this reason: because it deprives the American state of a critical tool for keeping a large section of the productive population down on the farm and working hard to pay for all those free pills and free hot pockets and subsidized rent vouchers.
On this theme, giving people in the GOP the opportunity to display their value to their masters is useful for both parties. When spoilers like Donald Trump earn high polls, it’s a sign that they’re not doing their job properly, that the cattle are getting restless, and that the political policemen need another ‘Benghazi!’ style shiny object to redirect their attention away from more important things.
It’s also important to remember that throughout American history, the parties that have been able to bring the entire country underneath its apparatus of economic extraction and cultural management have tended to dominate smaller groups — the broad appeal worked, as we know from the gradual introduction of new nationalistic ideologies which evolved from ‘America the WASP frontier’ to ‘America the shining beacon for Whites of all Christian denominations’ to ‘America the White’ to ‘America the universal colorblind ideal-nation,’ the political parties which have been able to assemble the most numerous and wealthy supporters have tended to succeed against those which have made more narrow appeals.
The American conservative movement is, broadly speaking, an administrative arm of the left that acts to consolidate the political gains of the broader leftist faction. They make sure that recalcitrant citizens get with programs affirmed in the 1940s, 1960s, 1970s, or at other points in time, to say little of planks of the program established earlier in the 20th century. They permit some quibbling over new developments in international leftism, in exchange for unquestioning obedience to the larger platform which has already been implemented.
In the end, democracies consume themselves, as federations become unstable and break into mobs made up of people without common interests. Creating political structures that create and maintain common interests among people is very hard indeed, and most fail to do so (democratic or otherwise).