I wonder what you base this statement on. As someone who has worked almost exclusively with Drupal, I have been always been conscious about being on an island, concerned about my lack of understanding regarding other frameworks, languages etc. Because of this, I am constantly looking for the signs that would indicate that Drupal is falling, yet I still have to find these. Admittedly, since I work for a company which has Drupal as its core business, I am biased.

To avoid this bias I was doing a little research for statistics. I checked the usage of Drupal core [1] and I found it somewhat misleading (e.g. there is a significant jump around the time of the release, so the statistics on such short term must be skewed due to test installs). Instead I looked at ctools, which is a dependency for several contributed modules and is the top used module [2]. This shows significant growth since the start of 2016. So it is growing, people are using it. But most importantly, the numbers for Drupal 6 stay the same. So it seems that people who have a stable website are happy with it, and new users are likely to jump on the Drupal 8 train.

Also let us not forget the same voices were heard when Drupal 7 came out, coupled with the unexpected lag of contributed module availability. With a lot smaller API change, people found they have to wait 6-12 months after D7 was released to start building Drupal sites. Contribs, e.g. Views has released an RC for Drupal 7 on June 17th, 2011 [3], when D7 came out on the 5th of Jan, 2011 [4]. Views is just one of the important contrib modules (now in core), and people had to wait 6 months to use it!

The contrib upgrade curve seems similar, if a little bit faster for Drupal 8. But having most of the important contrib modules in core, this impacts new builders less.

About the state of the spaghetti: frankly I don't think that customers care too much about it (after all, Wordpress does own a significant share of the market ;)). Developers do. Customers care as well, but mainly to the extent of maintainability and cost implications. And I think with personal bias aside, Drupal 8 is much better on this front, than Drupal 7 (although there is still work to be done, procedural code to kill), it does deliver a framework, which allows a wider range of developers to start working with it, using familiar patterns and frameworks (PSR-4, Symfony).

Long story short, I don't hear the swan song. But I'm happy to keep my ears open :)

[1] https://www.drupal.org/project/usage/drupal [2] https://www.drupal.org/project/usage/ctools [3] https://www.drupal.org/node/1192186 [4] https://www.drupal.org/node/1015392