Actually, I'd like to challenge the assumption that you need asset store plugins in the first place. In our humble opinion you don't need Asset Store plugins for Unity to look fantastic. We have achieved near photorealistic lighting and reflections in Unity, both in URP and HDRP (haven't tried built-in for a while) without using any Asset store plugins, in Unity versions 2021, 2022, 2023 and now in Unity 6.
I recommend to check out Unity tutorials and free samples, https://unity.com/blog/unity-6-graphics-learning-resources. Additionally, I recommend to learn about these keywords
- Baked lighting
- Light probes and adaptive probe volumes
- Reflection probes
- Post-Processing (bloom, tone mapping etc)
Good luck on your game development!