They've done good things in Ohio, and presumably other states, when it comes to fighting legal battles in favor of increased ballot access for third parties.
I also find your opinion that they should just infiltrate the Republican Party and try to change it from within, instead of trying to build a separate institution, ridiculous and amusingly American. As if the Republicans have and must always exist and no party has a right to ever dethrone the two-party system. Such opinions are why our political system sucks.
If you honestly believe a third party will rise and challenge the two major parties any time soon, you should have your head checked cuz it ain't gonna happen.
There is a difference between whether or not I think there will be a rising third party in the near future, and whether or not I want to go out of my way to discourage that from happening in every way I can. I don't think a third party movement is going to gain traction, but I at least want that to happen and don't go out of my way to talk sh*t about it for seemingly no reason.
Almost any time in American political history that one of our parties has undergone ideological change, it's been because a third party or ideological movement rose up and didn't take power themselves, but rather,
prevented one target or another from taking power. If Libertarians get 3-10% in any given election and prevent a Republican from winning, Republicans will take notice of them and start catering to their needs. That's how ideological change happens, at least here. No "infiltrating" will almost ever be successful unless there is actual, noticeable force in numbers. No change would happen if Libertarians just didn't exist.