I dunno, most of the difficulty in NES-style games is the fact that the encounter rate is stupidly high, Mother 1 included.
Obviously, this goes by a game per game basis, but I had great experiences with Mother 1, Dragon Quest 1, and Metal Max 1 on the NES. Even in regards to the encounter rate, well, battles are the primary reason I play turn-based strategy games to begin with. I know people tend to complain about trash mobs, but more often than not, I find random encounters to be an endurance test for how well your capable of managing your resources. Some games flesh out these concepts more than others, but when it works, it works. Dragon Quest 1 (NES) being one of the better examples of this. The way the campaign is balanced, it essentially works as an investment simulator of sorts. So much so that its no wonder Horii would immediately go on to develop Itadaki Street. Most RPGs generally tend to have the distribution of items via shops consist of a sole upgraded weapon type for one of your party members, same for armor/accessories. Dragon Quest 1 has multiple in one location, of each equipment category. This is done to have the player choose what investment he plans on making, with the severe punishment of having your cash reserves significantly reduced if your too stingy. Mother 1/2 operate on this same principle -- altho, not to the extent that I would like.
I get that encounters can be a nuisance in games like Skies of Arcadia, where battles are a mindless affair, with little to no short/long term resource management incentives; or especially punishments that would deter one from being a money/item hoarder, as many other RPGs have become. Games such as Dungeon Encounters and Disgaea 6 have - to my appreciation - went back to the drawing board, and have really thought out what makes these games great, and what the future of the genre (at least, for their franchises) ought to be.
And its unfortunate that games that have taken DQ1 as influence, have made many excellent ideas that are never fleshed out upon by other games. Pokemon makes healing free, sure, but the PP system is an excellent addition that is just a little too undermined in Pokemon given how easy it is... but no one else has ever found reason to try at it. And games like Helen's Mysterious Castle end up being more of a puzzle rather than a game where adaptation is generally required to transcend an RPG combat system, to a mere puzzle -- see Into the Breach as an even worse example of a game being devolved to merely a puzzle (as much as I don't like it, THAT is why Fire Emblem randomzies stats to the severe extent that it does).
Altho, all that being said, there is an extent to which I can praise Mother 1 over Dragon Quest 1. Both Dragon Quest 1, and Soul Shepherd (SMT:N's hardtype creators original game) have great balancing when it comes to challenging fights that are fair, but run into an annoyance that I think stems to the
primary issue most have with 'NES Hard' RPGs: the fact that you are not making minimal literal progress (traversal of the map, for starters) due to the difficulty of these fights. You often have to remain within a close radius of the starting town circling around for battles for far too long before being able to set off on your adventure proper (and continually repeat this process as well in each new zone). In essence, there is no flexibility to have short/long term resource plans due to how difficult an individual battle is, while - and this is important - not providing adjacent means of recuperating from said battles -- something games like Dungeon Encounters pull off immensely (as well as Wild ARMs 3 to a lesser extent, and Wild ARMs 5 slightly lesser).
Mother 1, on the contrary, lets you wonder the game world to discover things, while providing a decent challenge all the while, and this is especially where I bring your claim to task
lightbane . I understand that you cannot enjoy the game, and I also understand that battles are secondary; or even tertiary affairs for some RPG gamers, but I honestly think Mother 1 does a pretty good job - even moreso than Mother 2 - at striking a great balance between non-linear overworld exploration, and a decent amount of difficulty.