First off, dont give up. Second, I dont think critical thinking is the issue here- self confidence may be. We have all been there- its a new role and you need time to get antiquated with it. This section of the Google UX course focuses on ideating- https://www.coursera.org/learn/start-ux-design-process?specialization=google-ux-design
See if it can help. Reach out to colleagues and Dont give up.
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Good luck.