Sorry, but I just can't agree with this. Fallout 4 is literally nothing but "Kill, Loot, Return", as others have said.
Is Fallout 3 a fantastic game? No. Is it an okay RPG though? Yes. First of all, there's lots and lots of different ways to be evil. Nuking entire settlements, enslaving entire populations of people, multiple evil endings for a lot of the quests throughout the game. Fallout 4 has only 6 instances where you can actually be evil. Killing everyone in a settlement or town doesn't count, especially considering half of them are marked as "essential" for no reason everywhere.
In Fallout 3, though minimal compared to New Vegas, your SPECIAL choices mattered. It changed up dialogue, it changed how you could play the game, and it did indeed shape your character. For instance, a high Strength gets you a lot of bullying dialogue in case of low speech. In Fallout 4 though, the only SPECIAL that actually changes any dialogue is Charisma, and at best it only allows you to ask for extra money or maybe uncover a tiny secret about some minor character.
In Fallout 3, quests usually almost always have multiple endings to them, such as Tenpenny Towers or Blood Ties. In Fallout 4, almost every single quest ends exactly the same no matter what you do. There's no choice, no variety, it's, let's say it again, "Kill, Loot, Return".
The companions are far better in FO4 than in FO3, I'll give it that, but neither compare to New Vegas's dialogue-wise or personal quest-wise.
Customization-wise, the so called "improvements" to weapons don't really do anything worth noting, and most of them definitely aren't worth the parts it takes to upgrade. I feel like those upgrades were just a lazy attempt by Bethesda to cover up the fact they have less weapons than New Vegas, a game that came out almost 5 years prior. Can't tell you how many times I've seen some gun labelled "High-caliber bayonetted high-powered optimized assault rifle of the death knell" and it does maybe 3 more points of damage than the base weapon.
I could go on and on and on as to why I think FO3 is far superior to FO4 but I'll leave it at that for now. At the end of the day, I can still pop in Fallout 3 and get some enjoyment out of it. Fallout 4 is quite literally a succubus that just drains me of joy every time I attempt to give it another shot.