Principles and basic fundamentals are the same, tools have changed a bit.
The advent of reliable and affordable laser range finders is a huge change from 30 years ago. Add good ballistics programs to that mix, scopes that have properly designed turrets and reticles, and a Kestrel if you want to get wind readings. All of those make the math part way way easier to manage.
Now you can go buy a Garmin Xero Doppler Radar chronograph the size of your hand and get real no bullshit data on your ammo and what it is actually doing out of your barrel. So plug all that into your smart phone murder math app along with your other data like wind and range… you see where I’m going.
A .308 is still capable, but there are better solutions to longer distance shooting. Fortunately most of them are compatible with the nominal .470-.473” bolt face diameter of your .308 Winchester. You would only need a nice custom barrel in 6.5 Creedmoor, 6.5X47 Lapua, 6 Creedmoor, and a few less common chamberings. Everything else you have will probably work just fine. Add a range finder, maybe a Kestrel, download an app. Go out and apply basic rifle marksmanship fundamentals and incorporate data into your scope adjustments. You will find out very quickly whether the optic is up to the task, if it is keep it. If not upgrade it, I would rather have a $2500 optic on an $800 rifle than the reverse of that.