my intuition for this card is that, like transmogrify, it has a high skill ceiling and is also not very good. the thing about that, though, is that it kinda has to be good because of all the things that it does.
the other throne rooms seem sort of solvable, almost, get throne room when you have a high action density (especially with expensive actions and village scarcity), get procession in similar cases as long as the upgrade process has some destination, and get king's court if you have $7 and there isn't goons, maybe.
royal carriage is a better card than throne room in, like, the sort of situations that you aren't
trying to come up with right now, such as, you draw it with no actions, being the obvious one, and you don't have to cry until you watch the one futurama episode later today or when beck hits the high note in debra, ohoho. also, there are a bunch cases where procession is a problem that throne isn't, evident in most of the card rankings the community has to offer.
king's court is probably one of the best cards that there is, but not at adding to this discussion.
so royal carriage is demonstrably, like, an okay card. playing action cards is your method of being an agent and carriage lets you do that indiscriminately, and also that was a lie because the reason that it's good(?) is that you in fact use it very discriminantly.
i think royal carriage shines in kingdoms that have cards that cost more than $5, because you will be able to double them quite often if you want to for less money, and, more uncomfortably, in kingdoms that benefit from being able to get one strong turn to get the ball rolling, sorta like tactician i guess? what comes to mind for this, is, conspirator, things to stack up for on-buy (haggler, cost reducers/merchant guild, maybe horn of plenty counts) and maybe when trashing is hard to deal with (terminal trash-ones and cursing but cursers tend to make it hard to get to $5 and then spend it on a non-curser)
does any of that at all makes sense? how bad are my assessments? do you get carriage in the kingdom of, say, salvager, moneylender, witch, bazaar, carriage, hunting grounds? is tactician a good comparison? is it a good idea to forsake scrutiny with the card art? (yes)
thank you for your time