InDesign is showing pink boxes because Nirmala UI and Malgun Gothic are Windows system fonts and don’t ship natively with macOS. InDesign on Mac can’t access or render them unless you’ve manually installed them (and even then, it’s hit and miss depending on the font licensing and compatibility).
Use Adobe Fonts alternatives
Nirmala UI is available on Adobe Fonts - you may need to use this
If it's still not working then for Hindi
Adobe Devanagari
Siddhanta (Free Google Font)
Lohit Devanagari
For Korean:
Adobe Myungjo
Adobe Gothic Std
Nanum Gothic / Nanum Myeongjo (free Google Fonts)
You can activate these directly from Adobe Fonts via Creative Cloud.
Use Google Fonts
Google Fonts has solid multilingual font support. These are free, cross-platform, and often reliable in InDesign:
Hindi: Noto Sans Devanagari, Noto Serif Devanagari
Korean: Noto Sans KR, Nanum Gothic
Download and install the fonts, restart InDesign, and reapply them in your paragraph or character styles.
Ensure World-Ready Composer is active in InDesign (especially for Hindi). Go to Paragraph panel > flyout menu > Adobe World-Ready Paragraph Composer (and also set this in the Paragraph Styles)
If text still doesn’t render right, check the language setting in the Character panel to match the script. This influences hyphenation and shaping.