I think pretty much depends on what a person considers easy to work on. Anything pre-1990 will have very few emissions, carbs, no OBD port and be simple to diagnose and repair if you know how they work, you can easily do things like bypass cats or perform mods with no side effects and usually gain performance. Pre 90's vehicles also tend to get better fuel milage in stock configuration due to the lack of all the additional BS installed on the engines requiring more power to run.
Mid 90's-2005'ish have OB2 ports which can help diagnose issues and the vehicles are still easy to work on, they have more BS on the engines which is normally what is going to throw to code to begin with. O2 sensors, smog pumps etc.
2005-2015 have even more computers but a person can still do most of the work, you will have to use a code reader and also have to most likely do some programing and learn how they work to be able to work on them yourself. A lot of items including the speedometers, TPS systems, ABS and ECU's are SN specific and need to be flashed by a dealer or computer program to be able to replace them. A lot of this was done so the average joe needed to take their vehicle to a shop to get it worked on.
2015- Current, A lot of computer systems are integrated in these vehicles and if some go bad it could be thousands to repair, everything in these vehicles is tied to the computer, including the seats, things as small as swapping leather seats from the junkyard will throw codes that can't be cleared except by the dealer due to air-bag configs. IMO these vehicles are part of the new disposable society and will all end up in the junk yard with relatively low miles.
There is a lot of overlap in the timelines above depending on the manufacturer. Some vehicles like the Toyota Tacoma stayed pretty dumb clear up to 2015, essentially they were the same truck from 2005-2015. Others started changing much sooner and after 2020 everything went to the extreme with electronics.
I like 2000-2010 vehicles, they are still straightforward to work on but also have a lot of creature comforts of a modern vehicle. Coil over IFS on 4x4's, easily upgradable stereo systems to have nav without hacking the whole dash apart. Parts are reasonable, they are comfortable inside and tend to be well made still for the most part and seem to hold up to lots of miles.
I have had great luck with Toyota and Jeep, the Toyotas are on another level for the most part, they have some annoying maintenance items like timing belts but are super reliable when maintained and almost never have leak issues. Jeeps in my experience run forever but when they start to get higher mileage the engines, pumps, trans and diffs all start leaking.
I recently sold a 2015 Tacoma with 115K and upgraded to a 2005 Tundra with 290K, it runs like a top and has zero oil leaks. We also have a 2004 grand cherokee with 255K miles on it that I bought in 2004 with 13K for my wife, she drove it for 16yrs and my son drove it for the last couple.
IMO you can't beat a first gen tundra, plenty of power, will tow fine, is comfortable and they will go 500K+ miles easy with minimal maintenance.