And if we still have tanks in 2017 then it’s more than reasonable that X-Wings and TIE Fighters are in TFA.
Of course. We still have Mark I tanks from WW1 as primary tanks.
No, but our primary tank, the M1 Abrams, entered service in 1980.
Yes and Soviet Union collapsed in 80s ending the arms race and any serious competition. In Star Wars case we have the exact opposite scenario; the Empire’s monopoly ended after ROTJ, making the two sides more equal, increasing the competition and arms race between Empire leftover and New Republic. By the time of TFA, dozens of models should have gone through the evolution for each role (fighter, bomber, etc.). What we have instead is the exact same things we have seen in ROTJ. Actually even one step back, since we don’t even see the newer ships from ROTJ.