There was a bootstrap era, where everything looked the same. Then there was a materialUI'ish era, this was weaker in dominance because the design is more controversial and often downright bad in UX. Now we are in tailwind era.

Not hating, it looks and works ok and I understand spending time on custom design is not something you should optimize for as an early stage era startup.

But I do miss the times of mid noughts where people were playing with styles (css zen garden anyone?)

Let me know if you find one. You can design your website yourself by taking inspiration from other different websites but as a person who is not a web designer gaining consistency in your design is tough. Usually a template is not enough, it may help you with some scaffolding (such as setting a theme or fonts) but you need to have some knowledge about web design to at least make it look consistent.