honestly the page2 stuff someone mentioned earlier is underrated. ive seen way faster wins from going back to pages sitting at position 11-15 and just rewriting the intro, adding internal links from my stronger pages, sometimes merging two thin posts into one. those move quicker than anything new i publish.
the point about top of funnel keywords being dead is real too. AI overviews eat that traffic now so informational "what is x" stuff barely sends clicks anymore. i shifted most effort to comparison and "best x for y" type queries where people are closer to buying, and the conversion difference is night and day even with less traffic.
on the ad spend thing... idk, i dont think the ads directly pushed organic rankings, google says they dont and ive never seen it cleanly. more likely the extra traffic/brand searches/engagement signals helped indirectly, or it was just coincidence with other stuff ranking. wouldnt build a strategy around it personally.
backlinks still matter but nobody outranks weak content with links anymore. get the content + internal structure right first, then chase links. consistency over 6+ months beats any quick trick imo