To be honest I can’t recall when was the first time I used QGIS but it was probably when I was studying civil engineering about 2004 maybe? I think that a lot of persons have this initial experience with opensource as a way to avoid the licensing costs and certainly that was why I looked into it, ArcGIS is quite expensive and on top of that additional extensions are also extra money. I recall using QGIS 1.7 a bit more so that would probably be the year I really started using it more.
When I started using QGIS it was not so good (for my use cases!) mostly because even though I was a GIS user my primary focus was on map creation and the layout functions on QGIS were not so good back then, now they are pretty solid and powerful. As I transitioned into creating aviation charts initially it still missed the required functionality for many of the things we did back then but as we moved towards integrating Postgres/Postgis and Geoserver, QGIS was a powerful ally to edit features without requiring additional and expensive licenses.
Fast forward it is 2022 and it is now 20 years old! What an experience it has been watching it evolve from the clunky software from the past to one that I can now safe without issues would probably be on par or above of other COTS software, of course this will all depend on your workflow and requirements but pretty much it is an amazing geographic information system (GIS). It has amazing layout capabilities and I find that it provides greater flexibility that what I enjoyed when using ESRI products. Each one has their own merit and I do think that ArcGIS Desktop and Pro plus the rest of the ecosystem is quite capable but sometimes you have budget constraints and other times QGIS is a better choice in itself.
To mark the 20 years I have already made my donation, so can you! Donations (qgis.org). Also if you want to learn about QGIS and enjoy Youtube videos you can go to my channel and in this blog you can search for QGIS related posts.
May QGIS guide you!