I have to say I have been contemplating this question for quite some time now, especially with the 2020 election on the horizon. I remember personally working on the campaign for him the last election full with optimism for change. I knew some aspects politically would most likely remain the same, but I did expect some reform in aspects like Illegal Immigration and getting out of conflicts in the Middle East. Now after almost 3 years since he was elected what have we really gotten in return from our support, which for many has cost them friends and the risk of social and professional ostracization. We still don't have any new border wall built which was his main promise (he has repaired some old fencing and barriers but it is not the same). We are still in countries like Afghanistan and Syria, the latter especially where he has boasted this year many times that we are getting out but in the end one way or another one his advisers like Bolton or Pompeo later say the opposite (gotta protect Israel you know). Speaking of our "greatest ally", Israel seems to have been the main winner so far of his presidential term:
-Recognition of Jerusalem as the eternal capital of Israel
-The embassy move from Tel Aviv to Jerusalem
-Recognition of Golan Heights as Israeli territory
-The new 38 Billion Dollar deal over the next 10 years ( of course our 25 Billion Dollar border wall was just too expensive and unnecessary)
Of course today as well he sign a executive order that targets colleges that allow "Antisemitism" (as broad and ambiguous as they want to interpret it of course). If he could only take the time to sign an executive order targeting the indoctrination of Cultural Marxism in our colleges, or maybe sign an executive order stopping the media from defaming and ruining a person's reputation and life.
Besides the tariff policy towards China which I consider a success so far, just how successful has the "Make America Great Again" agenda been. Sure he signed a tax cut bill in 2017 and the GDP has been growing a amazing rate, but is that all these "conservatives" think America is defined by, it's GDP? Moreover would this have been any different than any other normal Republican who would have fought for tax cuts. Our fertility rate is still below replacement level, our families are still breaking apart, we have a rampant drug abuse problem, the middle class even in this high GDP is still disappearing, and we are still being replaced by endless waves of nonwhite immigrants.
I suppose we support him more by what he represents (or at least is supposed to represent) which is change from usual established politics, rather than what his policies have actually meant so far. It's also not like we have any better choice, especially with the lunatic batch of Democrats now in the race.