In his 2004 book on the Electoral College, George Edwards debunked the reasons for keeping the system as is, noting that (i) small states have little common interests with each other and are not a block that deserves outsized power in choosing the president; (ii) large-state citizens should not be disfavored because big states are not controlled by particular factions that should not be given too much power; and (iii) the selection of the president does not in any way promote federalism.
In other words, three rationales considered in 1787 in creating the electoral system are no longer based in reality, if they ever were.
So advocates against change need new reasons to keep the presidential selection system. To speculate, they might include:
1. No one thinks there is a way to change the system. So let’s just give up on improving the Republic.
2. One party or the other typically thinks the system advantages them. Therefore one party always blocks reform. Let's have short-term thinking harm the best interest of all Americans.
3. Some politicians don’t want to learn a different system. We have to tolerate their limitations, so let's not change a thing.
4. Some people like the voting rolls as they are, because true democracy might lead to different taxation, spending and law-making. Everything is now for the best in the best of all possible worlds.
5. Although all states have recount procedures, a national vote count potentially would require all states to use them to do recounts in a very close election, like the 1960 Kennedy-Nixon election. That was a long time ago but it could happen again. And it's too much trouble to have lots of recounts, when only the presidency is at stake.
Anything else come to mind? They spin, you decide.