I'm relatively new to the site, so I don't know if it's normal for expansions to not be listed until after release...
Additions to the site have gotten slower, and I'm currently attributing that to the greater numbers of cards/set and products in general (e.g. multiple variants of art, Art Cards, Secret Lairs, The List, Commander Decks for every set, etc., etc., etc.).
I scraped this site for how many cards were added per year (breaking out Secret Lair and The List into their correct years, and ignoring ~1600 cards I couldn't easily place, such as FNM, Media Inserts, Judge Gift Program, etc.).
What we get is a huge increase in the last few years, with 2019-2021 seeing more cards added to this site than the previous 7 (2012-2018) combined:
Year Cards
2021 7,281
2020 5,607
2019 5,035
2018 3,385
2017 3,320
2016 2,665
2015 2,163
2014 2,104
2013 1,758
2012 1,377
Are things being added slower now? Yes.
Is this frustrating at times? Sure.
Is it understandable given the product release pace? Absolutely.
Just sharing some data, and here are all the years in case folks are wondering:
Year Cards
2021 7,281
2020 5,607
2019 5,035
2018 3,385
2017 3,320
2016 2,665
2015 2,163
2014 2,104
2013 1,758
2012 1,377
2011 1,645
2010 1,436
2009 1,234
2008 994
2007 1,111
2006 1,055
2005 1,734
2004 898
2003 1,122
2002 789
2001 1,116
2000 881
1999 1,575
1998 1,087
1997 1,508
1996 1,054
1995 2,700
1994 1,332
1993 1,595
n/a 1,575
Please note that this doesn't necessarily correspond to when cards were added, just when they are listed as being released in the site (there are some errors that I did not correct, which I believe to be minor, like some Extras not aligning to their release date).