"My smartphone shoots better than this"
"It does look better, but I don't see much of a difference to justify the price"
It's flawed reasoning to ever say your smartphone shoots better. Your smartphone shot and processed it for you to some extent. It took all of the controls away from you and did its thing. The smartphone doesn't shoot better though; you just shoot worse with your camera. This is an issue of not knowing how to use your camera. If I have an iPhone 7 ($700 USD) and a Nikon D3300 ($400 USD) in the right hands the Nikon D3300 will take better photos every single time. If you're regularly seeing the iPhone 7 outperform than there's a bigger issue. Either something wrong with your camera or more likely you just don't know enough to use it well yet.
I realize I'm talking like its to you when yours is a hypothetical but hopefully that makes sense.
Next issue could be what are you using it for? I mean where are you looking at the photos? This is why your question is entirely too vague. If you're only looking at your photos on your phone and on facebook then it makes a lot less difference. If you look at them in print or even in high resolution on a large display then you'll notice a lot more quality differences. Here's a nice comparison of an iPhone 7 and a Canon Rebel. When looking at the thumbnails its pretty comparable but enlarge them. Look at the dog photos and the glass bottles. The sharpness and quality of the iPhone quickly plunges.
Cost: iPhone 7 around $700, iPhone 7+ around $850, Canon Rebel with kit lens around $450.
Flagship Smartphones don't in any way extend the lifespan of the phone. In 3 years it'll be old and ready to retire. Whether you do or are able to push past that point and keep going is another story but it'll be tough. Entry level DSLRs or Mirrorless or even Point-n-Shoots will last significantly longer. There's just less wear and tear typically since a phone you're using all day every day for the most part. There's less tech advances. Now to be fair there is some number of shots that starts pushing the limits -- 100,000 is a general base for DSLRs. You would need to take 3000 photos a month (which is a whole lot!) to hit that in the 3 years it'll take for your phone to die. The reality is most cameras can last a decade pretty easily, if someone upgrades its by choice not by necessity. With your phone its probably because the battery was dying, the OS was no longer receiving updates, the screen cracked, etc.
So your Flagship smartphone that lasts 3 years and costs $700 is about $233 a year. A solid mid-range DSLR (I'll use Canon 70D) that can last 10 years and costs $1000 is only $100 a year. Even if you want to replace your camera every 5 years bringing that cost up, you're also replacing your iPhone every 3 years. In 15 years you'll be replacing your iPhone 5 times for $3500. In 15 years you'll be replacing your 70D 3 times for $3000.
Any midrange camera will beat a smartphone in quality and in value. If it doesn't the problem is the photographer.