Overall I agree with this, I definitely see why Googlers are frustrated at having all of this framed as 'personalization'.
But broadly, I see three bases for objecting to these changes.
First is the lack of user control. Like many other people in this thread I often want to turn off or 'rehome' localization, not just for weird developer use cases but for obvious stuff like "I'm about to travel and want results for that location". Disabling session-based changes is a rarer desire, but comes up sometimes when a correction or topic change is interpreted as a refinement that's biasing results. Fortunately, resetting Incognito should manage that. (I've never actually wanted to bypass device type adjustments except for dev work.)
Second is inadvertent bubbles. It's easy to imagine content-neutral rules like "show fast and mobile-friendly pages to smartphones" correlating with a meaningful content difference, and the same for location. Hard to really blame Google here, but again it'd be really nice to have the option of a "stop helping" setting.
Third is Google-driven bubbles. Some of the DuckDuckGo examples showed effects like national newspaper articles on a search for 'immigration' getting reordered, or pushing above and below non-news sources. (We can't know if that was caused by location or device type, but let's look at the case where it was.) That doesn't look like basic localization, it looks like non-local results being adjusted based on user location.
This wouldn't have to be anything purposeful; if you add location into your training set and reinforce on the usual 'success' metrics (e.g. first result clicked, final result clicked), you could easily learn that people in NYC and Houston have different behavior patterns and display accordingly. It's open to debate whether this is a bad thing, but it's certainly not what most people (including the Googler who responded to the article) mean when they say "localization".