Your sentence "[...] out of 8 hours, I barely write code for 2 hours" contrasts with the next sentence: "[...] but this job barely leaves me any time to do so."

I am probably misinterpreting, but if you wanted to buy some time I would have thought this meant accepting this job to pay the bills, and then outside of work hours picking up other skills to create some interesting things, which sounds like the right way to build up your portfolio and skillset, especially if you've put in your required 8hrs/day in the day job.

I understand there are family commitments or other activities that may take up time, but in light of your implied situation (i.e. having to accept a less-motivating job to pay bills and buy time), you may want to consider either pushing for a new framework at work (which sounds like an uphill battle), or looking for another job.