It's always glad to see people inventing things for the better. When ICO's had its downfall several years back, people became wary of fundraising events involving crypto and that's when STO was invented, then IEO. So far, it has satisfied the taste of the community and it became a platform where people can again support legitimate blockchain companies (since they are also vetted by these exchanges) that helps to maintain the network, get low transaction fees and electricity consumption. The top 3 listed exchanges from the OP are all great, some good ones are Liquid and BitMax as well.