I also ,want to include the fact that in 5e, Advantage/Disadvantage plays a major role. If a character with +5 also has Advantage, that is a HUGE boost to chance of success. The Adv/Dis system is supposed to play a major role.
For example, my Gith Ranger only has +2 Arcana because he's not proficient. However, he's on a Ghaik ship. I, the DM, might give him Advantage on any Arcana rolls because his race is more familiar with mind flayers than Joe Half Drow. Even though the Half Drow has +5 Arcana, he doesn't gain Advantage.
So, a roll of 10 or higher is a 5 or higher for the half Drow but 8 or higher for the Gith. BUT, the Gith gets to roll 2 20-siders.
Flip the script. The Gith is proficient but the half Drow isn't. 5 or higher AND Advantage means the Gith has a super high probability of success versus the uneducated half Drow who has no familiarity with mind flayers at all.
Now imagine proficiency bonuses were higher WITH Advantage. It would be ridiculously hard to fail. They'd have to increase DCs and thus make the whole system more volatile. Low level characters would never have a chance ever against higher level ones... Not even a small chance.
