Eh? I dunno about you, but I ain’t rich. I want my tools to be reasonably priced for their functionality, whether it’s a computer, a car, a cordless drill, or a hammer.
That’s especially the case with computers, whose performance worsens over time as its hardware stays the same but software and websites get more bloated and new OSes stop supporting older hardware. Periodic replacement is a common practice.
Even if you’re made of money, there’s no sense spending it on things that won’t help your current uses (like a GPU for the OP) rather than just setting that money aside for a better replacement system (or piecemeal upgrades) in a few more years.
The OP gave a price range. The lower end of that can already meet their needs, with room to spare. The higher end of that is excessive for the stated uses. The OP’s needs are very, very basic. There’s nothing wrong with that, they just don’t need a superpowered workstation.
Yes, you can get one of these bad boys for $10,000+, but it’ll only be marginally faster for the things the OP is doing on an everyday basis. It’s like buying a Ferrari (or whatever fancy cars they make these days) for your 15-min commute to work on the local roads.
As for building it, sure, you can optimize parts here and there, but it only increases the maintenance surface that the OP has to personally handle, which is what they’re trying to avoid. And realistically, for a basic system like this, the only big boost they’re likely to get over a COTS prebuilt is going from a SATA to a fast NVMe SSD, but even Best Buy’s cheapest refurbs have that now. And going from their old mechanical HDD to a recent SSD of any sort is going to be such a huge boost already. The other stuff is mostly CPU and RAM, which might +/- 10-15% difference realistically, and probably not even that, especially single-threaded. If the OP doesn’t want to tinker, it’s not worth it. It might make sense for gaming PCs and professional workstations, not for the basic “I just need a computer for web and photos and spreadsheets” use case.