In light of https://www.drupal.org/node/2470679#comment-10001385 you are literally saying "D7 is fast, your custom modules and code need not to be so"
Slow down with the OOP kool aid, in PHP userspace it has a performance drawback.
This, of course, is much less pontificated than the "spaghettiness". Also, using functions instead of methods has *nothing* to do with spaghettiness, cyclomatic complexity has. https://github.com/symfony/DependencyInjection/blob/master/Loader/YamlFi... how is this not spaghetti?
Or if you think drupal_render was bad, then what will you say about https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Render%21... the Drupal 8 equivalent?
Yes, many Drupal 8 features are awesome but the design made it inherently slow and incredibly hard to comprehend and the caching hacks piled on top to make it fast again made it absolutely impossible to grok.