It's hard for me to know how unbalanced RCI missions may or may not be, because I have no clue what +10/20/30/... of any RCI value even means.
Times like this, I wish we could read the source code for ourselves to sanity check it.
Precisely.
There are very good reasons why Paradox produce some of the best grand strategy games available today, and chief amongst those reasons is the ability to view all present (and sometimes past) modifiers that are applied to any given number; they also do a very good job of imparting the necessary knowledge to understand how 'valuable' any given number is, i.e., you always know exactly what a number is worth to you.
TLF does the polar opposite of those things: it doesn't tell you what modifiers are being applied to any given number, and it doesn't give you any help in understanding the 'worth' of any given value. The RCI numbers are an excellent example of where, in my opinion, TLF gets it wrong: I've got no idea what modifiers were/are in play to explain why, for example, the Skylaxian Economy went up by 500% in the space of four years, and I have no clue what 'Economy +1905' actually means. (All I can say is that +1905 is 1905 times better than 1 – but actually is it..?! I have no idea!)
I'm a fairly intelligent chap and I consider grand strategy games to be my favourite genre (a genre now almost entirely dominated by various Paradox offerings) but TLF constantly leaves me baffled as to why something just happened, and I find it completely impossible to even part-way-accurately predict what's about to happen. I don't mind it when crazy things happen in grand strategy games so long as they can be traced, examined, and ultimately explained; in TLF that process is, by and large, impossible because every meaningful concept is agonisingly opaque. I suppose I'm just meant to 'trust the simulation' but-- well, I don't because I suspect that the maths is fundamentally wonky.
I like TLF – or more accurately, a really want to like it – but to my mind this game has a very long way to go before it call believably call itself a grand strategy game, and a very large part of that journey would be accomplished by simply (yeah, if only it really was 'simple') making the numbers transparent to the player.