Playing these again reminds me just how out of touch folks are when they say "stop complaining about the easy difficulty, Pokemon was never hard".
The trek through the first couple gyms is so much more rewarding than in newer games. Yeah, it's not hard, but it's also not painfully easy either. Playing casually I had to make a few trips to get through Viridian Forest, and I had to put a minor amount of effort into prepping for Brock. I was never really that close to blacking out because I'm good at the games, but I came closer than I have in a long time. All the recent games I've mindlessly plowed through, with no real strategy and no repercussions for my lack of attention.
Heals are plenty, items are less necessary, and I almost never get partway through a route or cave and think "oh man I might not make it!".
No, Pokemon was never really hard, but it used to require more of an effort.
I just restarted X to play through a nuzlocke in order to compare it to the nuzlocke I just started in Yellow..... It is absurdly easy in comparison. Not just in raw numbers (though those may be in your favor as well), but the entire design philosophy is changed to make things easier for the player. The rival you fight at the beginning of the game chooses the pokemon weak against yours, unlike older games. And your pokemon starts off with a move of its type instead of just tackle or scratch, so victory is guaranteed. Then they heal your pokemon right afterwards. In the first forest, there are far fewer mandatory grass patches to walk through, and your "rival" walks around with you, and talking to her heals all your pokemon. Poison doesn't hurt you at all outside of battle. So many little things like that. It's a pretty significant shift in design philosophy.