I achieved Level 120 in my sub. All the while with horribly low EXP. It just took 10,000 games.
Not by enjoying massive exp for sinking other ships
Not by playing hours on end during special events.
Not by purchasing Premium accounts.
I did it because I enjoy playing it simply for the fun of it.
When you play for the fun of it, the time goes by, your sailors get promoted, and you enjoy the game.
There is just too much emphasis on EXP or other "incentives". You don't need incentives if the game is fun. If it's a painful grind, a lousy ship, and no exp... Then Yes, you definitely want some incentives.
I have plenty of sailors at low-to-mid level that I've essentially abandoned. Not because of incentives (or lack thereof), but I find that a particular ship or nation is fundamentally boring compared to other ships or lines.
We don't need massive EXP increases.
In fact, I think the EXP for BBs is way too much. It distorts the true EXP you gain from other types (SS/CV).
If you're not playing for the fun of it, then play something else.