In Angband, resistance to acid, lightning, fire, and cold don't provide immunity to the side effects of that kind of damage - instakill monsters like wyrms will be reduced to merely extremely dangerous, and the risk of having spellbooks burned will still exist and cause problems. Resistances to other effects like blindness or shards provide immunity from effects, but still permit some damage.
This means that the tactical interest of elemental effects is preserved in the more interesting cases, and can be circumvented in the more deadly cases (spellcasters need total resistance to blindness to fight some monsters). This means some effects suffer this loss of interest because gameplay-wise there's no other choice. However, most effects remain dangerous or problematic throughout the game. Some (time, gravity) don't even have resistances available, and are feared by all characters.
Aside from racial resistances like dwarves being resistant to blindness, there are no permanent resistances in the game. With almost all resistances provided by equipment, it is very common to be faced with tradeoffs that pit two "essential" resistances/abilities against each other. The old and outdated Angband Newbie Guide would hold that you should wait until you have all the required abilities before venturing to certain depths (with the implication that you should eg. grind for poison resistance items before touching the last 60% of the dungeon).
The alternative is to keep descending and classify monsters as fightable or not depending on one's abilities. apart from eliminating the grind, the presence of monsters that mustn't be awake in the same room provides tactical interest by cutting off sections of the dungeon (at least for non-stealthy characters), making teleport unusable, and reducing the escape options. The result is to make monster detection, telepathy, magic mapping, treasure detection, and large highly-connected levels critical for success (at least for players who don't want to grind).
I find this method of play, where most resistances can be sacrificed if I have the ability to avoid dangerous monsters, a lot more enjoyable than the traditional alternative, which as you say is based on removing interesting aspects of play as the game progresses. Even with that playstyle, the effect isn't game-breaking because of permadeath. In cases where the early game is the most interesting part (because all gameplay elements are in effect), permadeath allows a player to experience more of the early game than they would in a "normal" CRPG.