Ecommerce is definitely not as popular as it was a couple years ago — I also thought FinTech would be really popular but our most popular categories are consumer & marketplace companies.
Consumer startups are really hard and they are all about retention & growth. The mistake a lot of founders make when building consumer startups is they build way too much “product” in the beginning, you should build the simplest but complete and lovable version of your product and launch fast so you can get real world feedback on what you are building, focusing on engagement & retention in the early stages. Engagement meaning “are users doing the behavior you designed for at the intended frequency e.g. two photos uploaded per week” and retention being “are your users active after 7 days / 30 days after they signed up”
For marketplaces, the key thing is how do you overcome your chicken and egg problem. My general advice is to focus on one niche within the market e.g. If you are building an artisan service marketplace focus on Plumbers or Electricians and ideally in one location e.g. Yaba or V.I and expand from there. You should always onboard the side of the marketplace that is easiest usually it’s supply side but during your “idea validation” phase, think through how you are going to get your customers doesn’t matter if it’s not scalable initially.