All the distance discussion depends on the length of the holes on the courses you play. If all the holes you play on are 300' or less, then if you can hit a 300' drive regularly, you should be okay - just focus on putting and upshots for when you don't hit 300'.
However, if you play longer holes or would like the "safest" drives, then increasing your distance will help your whole game.
I've been throwing 240'260' for years, being able to get to 300' a lot of the time. With the last year's efforts, I can now get over 300' regularly and sometimes out to 350' with my longest this year being around 390'.
Tonight I went out to my local course and threw a midrange or putter on 17 of 18 holes. I discovered I can park all 17 of them without picking up a driver. A hole where I had been throwing a midrange, I discovered I can't even throw a full stroke with a putter now - I have to choke it down. To me, that's increased accuracy, fewer big skip aways and should result in lower scores.
Now, even though I say this, I have to admit that I'm not a bad putter. I have my share of stupid misses, but 30' and in I'm pretty confident. I've been playing for years, so I've had lots of practice with upshots and putting, but never really focused on driving until the last couple years.
I've played recently with a couple guys who would get within 30' with their drive and then miss the putts - but these guys were using drivers, not midranges. Their max distance is <300' AND they're missing putts. To me, they need to develop both areas to really improve.
We have another course that is almost the opposite. One hole is >700', so if your max D is 250', then you're still looking at 2 max power and accurate drives plus a good upshot and a solid putt. Meanwhile, if your distance is 350', you're talking about two pretty good drives and a long putt opportunity. If you can crank out 1 accurate max D, then a good chance for a 3. All it means is that you find yourself more in a controlled distance more often than your max distance. Sometimes, that's the difference between 2 over and 2 under
I don't think the basketball analogy holds true for disc golf. You don't have to dunk to make a basket, it's all show and spectacle. You actually do have to drive a hole and there are benefits to your score if you can park a longer hole that somebody else can't. I know distance doesn't breed low scores, but practice does help with accuracy. Nothing comes without work.