This is true and is a big problem to saying how advanced areas actually was. The Scandinavians was well connected to the World and probably had very good knowledge about people like the romans and thus if they did something better they could simply try to copy it and military stuff is not straightforward that something is better or worse. Like light infantry can do very well against heavier armored enemies in rough terrain like at battle of Roncevaux pass in which lighter equipped Basques defeated the Franks which was Charlemagne's only defeat.You are talking like "tech level" is something that exists as an actual term in the real world, instead of coming up with a good counter or supporting argument you just say "hurt durr tech level", what is the point in typing something if you don't even have a proper opinion ready.
Often it is probably more like cost, tactics and suitability rather than lack of technology that encourage or limit the use of certain Equipment and troop formations.
Like France could have recruited large amounts of longbowmen during the hundred year war if they had really focused on it, it was not that they lacked the technology to make longbows, but there was other problems and issues that maybe did not make that Worth it.
Here it is mentioned that cost was a factor for the setup of a medieval army https://www.futurelearn.com/courses/agincourt/0/steps/8842
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