What are top no-code tools that lack extensions?

Off the top of my head, Alteryx is the market leader. It's pretty good but I don't think it supports XML or json (otherwise you could basically build a no-code web app).

The only other one I've tried it MS Power Automate, which is pretty underdeveloped. Lots of opportunities if you want to develop add-ons and extensions but I don't think anyone uses it for anything other than automating SharePoint and Outlook and other things in the MS ecosystem.