I am one of those weirdos who actually gets a thrill from filling out an excel sheet with XP awards and doing the math while recapping session events. So I personally never understood that complaint as to me none of the math to figure it out seems hard to me. In fact, before the days of access to a spreadsheet, I did it using an accountant notebook and still loved it.
As for what I give XP for, defeating monsters mostly (whatever form “defeat might take,” like killing, routing, forcing surrender, tricking, befriending, etc), but I also give XP for attendance 10 xp/level/session up to level 5 and then 25/level/session after that. I give XP for achieving specific goals in an adventure, and a bonus based on a percentage of total XP determined by how well the PCs completed the adventure (ranging from 5% to 30%). Everyone gets an equal share of XP as long as their character is present.
Lastly, I only award XP at the end of each adventure or module, so that can be every 4 to 6 sessions or more. Heck, one of my current groups has not advanced a level (they are currently 5th) since October 2022 and I have not awarded XP since July 2023.