It's hard to really say what makes it special. What makes the Mona Lisa special? Or what is so particular about the Eiffel tower? Or the old Die Hard movies?
This game released barely more than 20 years ago, yet we can already call it a relic from a bygone era, when video games were passion projects, and labors of love. It was a simpler time, where smaller teams of dedicated, talented individuals made games that they wanted to play themselves, and weren't burdened by sales targets, excessive monetization and ideological intrusions in both their creative works and daily lives.
My childhood was in Sims 2. Any successive sims games from that I just waved off dismissively with zero interest in anything that came after, and I really can't say why. I just didn't care much for them. Maybe it was feature bloat, or maybe DLC spam, either way, number two is the one I got stuck with... until the original CD I purchased it on was no longer usable and a replacement was nowhere to be found.