I think it really depends on the type of riding you're aiming to do, and what really brings you bike joy.
I started riding trail bikes in '98/'99 on a hard tail, like pretty much everyone did at the time. About a year and a half later I started getting into suspension bikes which led directly to bikes with more travel and a lot of DH racing for around 5 straight years. Then succumbed to a reeeeally long stint of post-secondary education where I only had a trail suspension bike and could barely even buy parts for maintenance. As soon as I started getting back on my feet, I bought a cheap Chromag frame, built up with whatever I could find, and realized that I still love the experience of riding a hard tail. With a background of spending 8 months a year on a DH bike, bringing one back into the fold made me realize I really love smashing trails with 200mm of travel, huge brakes and very soft tires. Yet I still spend most of my riding time on my 160/150 trail bike, which I absolutely love.
All this to say that we've never been in a better place to have one good bike that can manage most of the riding out there. But if you get more fun from the specific aspects that different bikes provide, it can still be very worth it to have the "right tool for the job". It's also nice that, after the big investments are over with, the maintenance costs tend to stretch out pretty well when you're spreading the riding hours over multiple bikes. And if one goes down with emergency repairs needed, you just grab another one, and go have a slightly different kind of fun.
I didn't just dump a irresponsible amount of $ to build my quiver, I did it slowly over time, with value in mind. Hard tail was fab'd by a friend, and a mix of old/new parts went on there. DH bike started with a 26" frame for a great price, half the parts were from my old 2008 DH bikes, but a great fork and 27.5" front wheel went on there and it's a lot of fun. 160/150 bike is the newest of the lot, first brand new bike I've purchased in 13 years, and purchased just pre-Covid boom.