This is something that has been a consistent issue since the game has launched.
We seem to have had a ton of F2 kitcar events recently.
Just did the F2 kitcar stage in Australia today (25 April), then did the NR4/R4 daily in Australia, and it was exactly the same stage 😪
Then today we also have a 'bonus' event which uses Group A (free choice, not just limited to the Legacy) in Argentina. This is not 'bonus' at all as my understanding is that the bonus events are supposed to use only DLC cars/tracks.
And that has also been an issue for a while now, with tons of bonus events not being 'bonus' at all.
Related to that is the incorporation of the DLC - 50% of the game is DLC, and yet there seems to be less than 50% incorporation of it into the community events.
Really hope these issues can be looked at and addressed before the final patch.

the locations are random, the weather is random. and the car classes are random but tweaked. actual mathematical randomness doesn't always generate the pure variety we expect when we think of randomness as a concept.
Killarney and Yas Marina (and Lydden, Estering, and Bikernieki too actually, but apparently you haven't noticed those) have popped up more often recently because there are always (at least, since the game was made free on PS Plus a month ago) two Promo community challenges every day which always (as far as I can tell) use DLC locations and base game car classes (the point is that they allow people who do not own DLC locations to try them out, but cannot do the same for the cars outside online MP). one of them is is always RX and the other is always rally. there are 5 DLC RX locations and 7 DLC rally ones. RX almost always uses the one class everyone wants to play (ie, Supercars) whereas rally can be any class (several of which some people use less, whether it's Group B or H1/H2. people clearly have more varied tastes and capabilities here) so it's natural that the RX tracks seem to get overused.
among the Bonus (Daily) challenges, one of the four is always RX, and it uses any RX location in the game. that means it's possible for there to be 2 RX events in the same DLC location one day. it doesn't happen very often, but sometimes it does, and people complain when things like this happen, as if randomness doesn't generate coincidences. it does. if you run a randomness generator enough times, it is guaranteed to create coincidences.
let's look at your example of getting one particular RX track in the rain twice in five days:
there are 5 DLC RX tracks in the game. probability of getting Killarney in a Promo challenge is 1/5 (20%)
let's say for argument's sake the algorithm picks rainy weather 33.3% of the time. probability 1/3
so the probability of getting Killarney in the rain is 1/15. (1/3 x 1/5)
from Tuesday to Saturday, there were 5 Promo RX events. 1/15 x 5 = 5/15 = 1/3. so there's a 1/3 chance of this happening in any given 5-day stretch.
but that's not all, because you need to include the Bonus events too. 1/13 RX tracks multiplied by a 33.3% chance of rain equals 1/39 chance of getting rainy Killarney on any given day; multiplied by 5 for 5 days equals 5/39, which is 12.8%
12.8% + 33.3% = 46.1%. so a 46% chance of getting Killarney in the rain in a Daily challenge over any 5-day stretch.
finally, divide by 2 (because you need 2 instances of rain + Killarney, not just 1) and you get 23%.
that's pretty high, isn't it? on average, that's nearly 1.5 times per month, just for that one specific track.
now, before I get 5 people telling me the numbers are made up, yeah that's the point. this is just a thought experiment to show that randomness doesn't always generate occurrences that we think of as "random". because us humans aren't as good at estimating probabilities as we think.