Why do the early 1990's feel so different than the late 1990's?

Grunge.

OP this is true of every decade. The 60s and 70s are two examples. Both started out looking/feeling strongly like the decade before and both were totally unrecognizable 9 years later. Compare 1961 with 1969. Everything had changed completely, fashion, music, film, politics. The 70s were the same. 1971 had Vietnam, Nixon, "women's libbers," etc. by 79 were were hurtling into Reaganism, women in the workforce were totally normalized, and disco, a genre that was virtually unknown in 1971, was on it's way out after peaking just a year or two earlier.

Culture moves fast and 10 years is a long time.

Technology grew during the 90s. The internet and cell phones, for example, surged and became popular as the decade went on.

Kurt and that damn shotgun.

R2 the 2000's felt the same, like one long hangover.

2000s contained nothing original except people dressing like trash. Everything sucked. The 9/11 era.

[quote]Culture moves fast and 10 years is a long time.

It as slowed considerably.

We're all basically wearing the same clothes we wore 10 years ago. Right I'm in a polo shirt, no pleat kaki pants and Adidas trainers. Just has I would have 20 years ago. (and fortunately I take the same size)

This is a 2010 BMW. It's 15 years old! Does it look any different from the cars of today?

It's every decade. Culture changes in 5 year cycles. Technology also plays a big part and moves very quickly, too. The major cultural shift in the 90s was the rise of a widely accessible, commercially-oriented internet. People who had never even used a computer were buying them for the first time to get on the web. No one had seen anything like it. It changed everyone's perceptions.

A similar thing happened in the 2000s with smart phones becoming ubiquitous at the same time that social media was taking off and becoming a daily feature in most people's lives. This type of sudden, new, direct connection to the rest of the word, driven by technology, will inevitably change the culture in a short period.

Just look at this decade. We started just as Covid took over, experienced a massive global pandemic for the first time, saw a political flip to Biden, and now 5 years later, everything is totally different. There's an understatement for you, but it illustrates the point. Every decade has two distinct acts.

My adorable millennial nephew grew from a six-year old kid reading encyclopedia Britannica in1992 to a guy with his own website in 1999.

The early 90s had grunge . The late 90s had Britney, boy bands, nu-metal, etc.

This is a little bit off-topic, but it saddens me that the term or expression "the gay 90s" was never embraced by the gay community during the 90s. I for one, had the best time, and it's partly due to being 30 to 40 during that decade

Design towards the end of the decade tipped towards a lot of dark colors, metal, and glass to ring in the millennium. Anything that was perceived as modern and futuristic was popular.

But you could say the same even about the 80's. The early years of that decade, when it comes to popular culture, were more gritty, infused by the cold war dread and the early days of the AIDS epidemic. By the end of the decade, everything was far more glossy, sexualized, and hedonistic.

Silly Y2K angst

Culturally, yes---huge differences. On a more material level---not really. Obviously there were differences but in 1999, all of them were viewed through the prism of culture. The personal computer and internet just seemed like fun, interesting things that largely were not integral to your day to day.