Well there's a few reasons you might think it's way easier:
1. Oh. My Gosh. Playing this game in 60 fps at 1080p is life changing. I can actually react to stuff and see hazards coming up. I'm honestly not sure how I even finished this game on the N64. It's loads better than 30fps with frame dropping at 480i . It's so silky smooth I don't think I can ever go back to the N64 except for nostalgia purposes. So yeah, WAY easier to play on that fact alone.
2. You're older (I'm guessing you played this in your childhood). This game really isn't that hard, but as a kid it was rough.
3. Combine both 1 and 2.
That's my take on it. But yeah, go back and try and beat your times. It's fun to try and whittle down the track records. Plus, most don't know this, but there's a cap to how you can upgrade your pod on a playthrough. You can only earn so much money and once you finish, however you upgraded it is what you're stuck with. Try re-playing with an emphasis on speed upgrades, or accelration upgrades, etc. Try racing with a different racer you've never tried before. It's a simple game for sure, but loads of fun for those of us who spent HOURS of their childhood into this both personally and with friends. I gotta hand it to this game, it's a LOT of tracks for what it is and when it was made.