That might be true some of the time, but we have items that give extra bonus actions and such, making dual wielding scale very well.
3d6 + 15 + 3d6 round 1
4d6 + 20 + 4d6 round 2
Only two items so far I can recall, both of which are conditional about how they grant that extra BA. One you have to be at 50% health and the other you have to use a fire spell so not ideal for a ranger anyway. I guess if you have a high elf cantrip? But then you are sacrificing your main hand for a firebolt that scales off of what's likely your dump stat (int). So the situations you would get these extra bonus actions are rare. Not really ideal items to build a ranger around. Meanwhile at level 5 without them, you will ideally be making 2 main hand weapon attacks to every one off hand attack (assuming you didn't have to hunters mark and can even use it). Seems better to add the +2 from dueling to that main hand that you consistently hit with instead of the +2 going to the offhand with two weapon fighting which isn't attacking consistently because of hunters mark application/jump/shove/etc. Plus being able to carry a shield boosts AC. You can also use a weapon that isn't light for a 1d8 (rapier) instead of a 1d6 (scimitar) Add in a potion of speed or a haste spell, both of which are easily acquired, and you can get four main hand attacks to only one off-hand (haste grants an additional action no bonus actions).
Personally, I think because of how reliant on bonus actions dual wielding is, it's best left to rogues, thieves especially. They might not get the fighting style like martial classes, but they can consistently get in an off hand attack every turn while still being able to do something else (potion/shove/jump/etc), or make two off-hand attacks for every one main hand attack. Certainly not saying dual wielding ranger isn't viable if you want to do it for fun, but it's a poor fighting style choice compared to the others mechanically speaking. Hopefully they adjust this a bit before release. If you could consistently land the off-hand it would probably be the dominant fighting style for rangers (assuming hunters mark) and more viable on other marital classes. Till then I would advise people to pick dueling, archery, or defense over it.