Yeah it's very challenging to see how the shows are actually doing - the few statements they've made are all obviously of the "this show smashed streaming records!!!" nature, but then you wonder why the services seem to be tanking and getting sold off, and why control of the franchise is being handed to a new party.You're right about one thing that it's hard to get the correct viewership numbers nowadays, Netflix started this trend and every other streaming service followed suit.
I did find this though am not sure how valid or accurate they are: https://flixpatrol.com/top10/paramount-plus/
From the deepest dive I did into this months ago, I got the impression that Discovery was considered a huge success in that it kept getting people to subscribe to CBSAA every time a new season dropped, and the first season especially drew in a huge crowd (though exactly how many people subscribed, and if they stayed the whole run, is ambiguous), but whether or not Picard and SNW have performed well is much more opaque; Paramount said they were very pleased with SNW when it started but it does seem like by the very few metrics we have, it's started to lose steam.
Most of the positive indicators are things like "we're pleased with the show's performance" and "this show's debut caused a huge subscriber spike", both of which don't indicate a great deal.
