I'm 25 and same. In high school (circa 2015-2016). In a developed country. Now that I think about it they probably had trouble sourcing the specialty incandescent lightbulbs to keep the damn things running (those had been banned from sale for years in the EU). ¯\_(ツ)_/¯

Many teachers just had really old slides they clung onto (or coursework in general... I vividly remember a geography class with grainy photocopies of maps with the Iron Curtain still on it, over 20 years after the fall of the Wall). But even if the teachers did want to show a video or sth, there were like 3 projectors for the whole school at the beginning, then it slowly improved to the point that most (but not all) of the classrooms had a projector. Some got lucky and it was overhead, and some even luckier with an overhead projector and a proper fold-out screen (other times we had to decipher a powerpoint slide against a dark green chalkboard...).
Must have been around 2014 that we last used the bulky CRT-on-wheels.

Part of the problem is each of those handful of awful "smart" boards we got that nobody asked for probably cost as much as 10-20 projectors and the school threw all its money into that. I'd be curious to know whether it was due to corruption, or non-relocatable funds, or just really good smartboard salespeople.

Shit, I'm old enough to have done research using actual microfiche.

Not much under that, but I remember them. I remember them more than slide decks.