do positions really matter now a days? so many of these players are interchangeable, even more so if they can do more than just slash or just shoot....it's nice to have versatility.
They still matter. It works like this: You still need ball handling, passing, playmaking and some speed. You still need in-between size guys who can defend, score and shoot. You still need big guys to rebound and handle the paint.
Sometimes you get guys who are of good size and can do many of those things themselves. People confuse teams with those players as showing positions don't matter. No, it's exceptional players who make you more flexible at other positions, but you never succeed without fulfilling those jobs/skills that have long existed at the traditional positions.
So, in regards to Burks, his size at SF matters just because there's Durant/Harris/George, etc. You can go two bigs and three guards often. (That's how the Pels finished the season on a tear.) But eventually you face the true SF who does the SF things and you have no real SF to deal with the size/speed combo.
As for a recent example, part of the reason the Kings beat the Sixers is because Philly is short on typical PGs. They often had TJ McConnel or a non-PG on Fox and they couldn't contain Fox at all. If it wasn't Butler guarding Fox then Philly was in trouble. TJ is the closest they have to a PG, but he's not that quick and Fox really broke him down and every other guard that Philly threw at him. It's also why Philly is probably still looking for a PG before the deadline.