Frame challenge: it is "small tech" not "low tech"
The technology deep inside Pangea 2.0 is superficially low tech, but actually comparable in "advancement" to the coasts.
Science and engineering has generally advanced throughout human history IRL. The "dark ages" weren't a time where technology got lost, they were a partial stagnation. Not to say they were fun to live in: new ideas were dismissed and the social hierarchy was steep and stifling. Most "lost inventions", such as "roman concrete", aren't as good as they are made out to be. A large-scale loss of practical knowledge is very rare.
As humanity advanced we replaced stone-tipped tools with better alternatives (stone itself is still used aplenty). But correlation does not mean causation: coast-dwellers would see "stone-tools" and think "primitive" (assuming the coastal people had their own stone age a long time ago). So how can we build a plausible "advanced stone age"?
Big tech requires big resources
One way to define "technological advancement" is how efficient the technology is in terms of producing goods and services per human-hour of labor. This definition is difficult to make precise because one can't easily compare how valuable "goodA" is compared to "goodB". But it is still useful as a general guide.
Each "level" of technology requires larger and larger "factories" to produce, with modern fabs costing $20 billion. In remote areas it is more efficient to be self-sufficient. Stone tools and grass huts are unbeatable in this regard. A slightly inferior tool that is locally produced could well be more efficient than trying to set up trading logistics with outside society.
You still could benefit from modern knowledge: in particular germ theory and nutrition. A little soap made from wood ash and tallow and boiling drinking water goes a long way toward keeping diseases at bay.
Why use metal when you have nanotech?
Admittedly, even a tiny amount of metal goes a long way. But self-replicating nanotech is far more advanced! The coastal people call it "biology" but they have less of it compared to your rain-forest ecosystem. Limpet teeth have amazing strength, hardness, toughness, and won't rust. They are unfortunately too small. But a larger organism with a similar lifestyle may do, more so if it is bred to have harder-faster(growing)-bigger-stronger teeth.
1% high tech
What if you have a small amount of trade with the outside world instead of being completely isolated?
You life is mostly without electricity: your mud huts don't have outlets and windows are the only AC. You hunt with spears. But you still have cell phones with a portable solar panel to charge them. Which can also turn salt into bleach, a very energy-efficient source of drinking water.
Not better or worse, still very different
Why do we still work so hard to support a week of living expenses? Can't the machines do most of the labor for us instead? There are many possible reasons: population densities, uneven wealth distribution, inefficiencies in government and businesses, higher expected standard of living, and more. Regardless, as a general rule, people still struggle to get by just as much today as the mammoth era.
But there is large trade-off in both directions between 12000 years ago and today. You exchange infectious diseases for diseases of affluence. The modern world has wonderful technology. But said tech also generated an excessive amount of celebrity: A few famous people get enormous attention and swim though oceans of paparazzi. This steals audience away from the local street artist. Similarly, markets are increasingly winner-take-most and the artisan gets squeezed.
It's such a culture shock to move between these two societies. To fend off an unfamiliar set of problems or make use of such foreign opportunities is very hard. "Uncontacted" people suffer if they enter modern society (not just from disease risk) and we wouldn't fare well in theirs either.
If life is different but no worse in the "stone age", and the switching costs are huge, why modernize?