If you’re taking damage from a ground effect, that is a result of mispositioning, not build, no? I can’t think of any ground effect dot that can’t be avoided off the top of my head.
If you’re taking damage from an ailment, these are always applied by taking some sort of a hit - meaning it’s not unavoidable damage, it’s part of the damage from the originating hit, just dealt over time.
There’s definitely things that are meant to have defenses to help mitigate, and there’s things you’re meant to use positioning to deal with - these types of attacks are mostly telegraphed.
Build planning and adjustment is an intended part of the game - not just offensively. It’s an important part of the depth in theorycrafting to strike the right balance between offense and defense, and do so in such a way that depends on the particular build. So while I do understand that they can be boring in use, their interest driver is in theorycrafting rather than play.
There certainly is “unavoidable” damage, but again, this is because build planning, thus choice, is intended as a significant part of the game. This is unlike say, a souls-like, which is almost entirely about mechanical execution. Having unavoidable damage means it’s another angle to take into consideration when planning. How will you survive it, and recover from it? There’s different answers to these questions, which again is there to offer depth to theorycrafting, and making characters more unique, with deeper interactions. In other words, a significant focus is on choices made, rather than mechanical skill.
That being said:, mechanical skill isn’t ignored either. With 1.1, we are introducing an Evade mechanic, which will certainly help lean into your preferred playstyle.
Actually, I find quite often the answer is no. Because of how our resistance system works, as previously explained, other defense options can actually offer more value than finishing getting resistances to cap. If you have to chose between being at 50% resistance, or having 30% increased health - the health is generally actually the better choice. Because many players are more familiar with resistances in other games, they will gravitate towards capping resistances, but I see as players have been around a while, they start promoting not to be concerned about capping resistances, and that other options can offer more value.