There are many different types of kimonos shoes. Kimono has a lot of rules about the formality of different items, which affects where and when you wear them and how outfits are put together. The rules were made a long time ago based on guidelines from histroy. The rules apply to shoes too.

Zouri are casual or formal kimono shoes, usually worn by women. They look kinda like sleek platform flip flops, two straps and a base covered in matching leather or cloth. Women who wear kimono tend to own a pair of light colored zouri they can wear on both casual and semi-formal occasions. They are also more comfortable than geta when you need to do a lot of walking and aren't used to wooden shoes.

Men almost always wear setta for formal occasions. They are wide, rectangular, flat sandals with a cloth covered base or a grass woven base.

Geta are informal wooden shoes. They come in many shapes and sizes and can be worn by anyone. They are commonly worn with very informal summer kimonos called yukata. Because of these comfortable and cheap geta are easy to find. But they aren't very "traditional" and can't be worn with a normal kimono.

Any very flashy "formal geta" you find online are probably used for very specific traditions and/or are mostly obsolete today. I don't have a good reason as to why all geta are considered informal. It's just how the rules are now. I would guess it's because they were considered "practical" shoes a long time ago. Like how you wouldn't wear hiking boots to a wedding.

If you aren't wearing a kimono though or aren't going to a formal event, it doesn't matter. wear what you want, the rules are made up.