My 1-year-old MacBook Air runs 1440x900 with 8 GB and it cost >$1.000 IIRC. So neither "very old" nor $200-$400 range.
So yes, the innards of your 2017 MBA are very old. It has Broadwell generation (circa 2014) CPU/GPU, and one optimized for power draw at that (i.e. a slower one).