No, addons exist because the base UI is that way that it is. The base UI came first, didn’t provide the level of information required for optimal, high-level gameplay, and the community filled in the gaps through addons.
Then, instead of taking notes from the community and integrating features that millions of players obviously wanted because they were downloading addons to provide, Blizzard did nothing for 20 years.
Case in point: when M+ was released in 2016, the PGF addon (Pre-made Groups Filter) was released a few months later. It took Blizzard until 2024 to implement their own native filter parameters into the group finder.