I think some people would have the same doubts as you, including myself. Not to underestimate them, but from our experience in La Liga, that teams that can surprise at the beginning of the season they will not be able to maintain until the end of the season, and that always happens, and maybe we can see from the past few seasons that there are always teams that can provide a surprise but at the end of the season it is still the 3 teams that are in the top 3, Real Madrid, Barcelona and Atletico Madrid. This may also be felt by other teams, one of which is Girona who are now at the top of the table.
It's really interesting that the trend is almost taking a different shape from the usual as Girona has successfully sneaked to the top of the table without people noticing until they got their and attentions were now draged to them because they don't usually get to this point most seasons.
Barcelona is looking like the only team amongst the usual big three you did mentioned that will be Left behind this season probably due to their too many crisis they are facing since the season started, they have been good until recently they started looking average with their performance but hopefully they will get back on their feet, Atletico Madrid has really been hitting hard this season trying to find their way to the top but having little hitches along the way but they can be very sure to qualify for UCL by the end of the season.