That CrowbCat video bugs me because people won't understand WHY all the things they are looking at were changed. The saddest thing was the ditching of w_models and v_models and instead switching to c_models so only one model would be used for first person and third person. It ruined tons of animation mods and made all the guns look different/worse because they generally used the w_models which were less-detailed (holy crap the flamethrower got devastated). This also broke a lot of the animations for the guns as you saw. The reason for doing it is to make it easier to work with only one model instead of two when making weapons or changing things and whatnot. The reason a lot of the guns look shiny is because they forced specular maps on all the guns that use skins (aka all the default weapons barring some) even if the stock counterparts aren't supposed to be shiny at all.
The lighting changes on 2fort and stuff are result of compiling the maps differently on hammer. Could be because of different settings used or just hammer being a piece of junk, probably both. You can no longer move the weapons with explosions because they don't want some person to try and pick up a weapon only for it to get blasted away, probably (also less physics is more performance).
Also there's a lot more graphics settings that have been added to current tf2 that aren't in the options that he may have on or off. There's mat_phong and new tf2 limits the use of mat_picmip (originally because it crashed a mac user if they changed it, why they haven't reverted this change after 7 years is beyond me).
Yes, a lot of the stuff he shows does look worse and I'm not excusing that because it's sad, but at the same time people need to understand a lot of the stuff isn't intentional (does that matter really? probably not...) or should at least know what they're complaining about.