First thing I do in a new app or new web service is click all the stuff, try and get a lay of the land and understand the UI metaphors. It's much harder to do if there is a twee, condescending guided tour "hyuck hey there champ didja know the gear icon that says Settings next to it is where you can change some settings?" stopping me from doing that, and names hidden behind hover popovers and crappy monochrome SVGs of....shapes to serve as icons.
I am very unlikely to need every part of every tool, app, or service I use. I need to do one thing with it right away, and I need to find my way there and experiment to see how it works. I don't give a shit if I can have it waft my farts if I'm trying to compress a gif or something, the fart-wafter button just needs to be clear so at a time when I go "huh what does this do" I can figure it out non-destructively to see if I'm interested. If you need a big popup saying "We just added the Fart-Wafter! Want to know how to find it?", you've failed, utterly.
The other side though is sometimes even more important it's what this thing does as a high-level introduction so you can understand all the things you're supposed to be able to do depending on the software this is some sometimes not obvious and that explanation can be really helpful to understand all the things you're supposed to be able to do and thus plan to use all those features.