After researching this topic, this claim is true. However, this claim could have been supported by a better-suited article. The article linked mainly speaks of kids' shoes and which ones are worth your money. This does not support the argument that Nike has decreased their quality, even stating "Nikes feel softer and flexible than some".
According to Zack Schlemmer from SneakerFreaker, he claims, "Nike’s quality and comfort seemed to decrease on their retro-style sneakers with cheaper plastic-y leather and smaller Air bubbles, consumers began to turn to other brands." This is true because, as the demand for certain sneakers goes up, production is rushed and made cheaper. He included an example of the cheaper material that they replaced it with, which makes his argument stronger.
To support the argument that they decreased the quality as the demand increased, the production. The Campanile states, "compensate for an influx in consumers in the sneaker community, specifically in the Jordan line, resulting in less exclusive releases and also poorer quality in the construction". The rise of popularity caused Nike to turn to cheaper alternatives, which caused the post of this claim as consumers noticed the difference.
Another article, which you can check out for this topic, is The Lance, as they have an in-depth explanation of the quality decline. One quote claims, "materials on different models are severely lacking in quality and quality control."
In conclusion, this claim is true but lacks evidence.
Sources:
https://www.sneakerfreaker.com/features/why-nike-stock-down-revenue-loss-explainer/
https://lance.mcquaid.org/12833/opinion/does-nike-value-quantity-over-quality/#:~:text=In%202020%2D2021%20Nike's%20Quality,Nike%20value%20quantity%20over%20quality?
https://thecampanile.org/4049/lifestyle/the-decline-of-nike-in-sneaker-culture/#:~:text=In%20the%20past%20decade%2C%20Nike,not%20suited%20towards%20casual%20wear.