Are there any alternatives?

Yes. You can configure a nearly identical machine from a wide range of vendors, though most are more expensive:

　　~$2,500 HP Omen 30L — The closest competitor to the Aegis RS 12, but lacks DDR5 support. Includes a much nicer toolless case, though.~$3,000 Origin Neuron — Free of bloatware and packed with extras for gamers, though comes at a hefty premium.~$2,200 Asus ROG GA35DX — A similarly priced AMD alternative with a Ryzen 7 5800X, but the build quality is worse and the case isn’t as flexible with upgrades.

How long will it last?

This configuration should last the next five to seven years without issues, especially with Nvidia’s DLSS upscaling tech available. The Aegis RS 12 uses standard components, so you can continue upgrading it until it’s the Ship of Theseus.

　　

Should you buy it?

Yes. In this rare case, MSI is offering a prebuilt PC that’s cheaper than building it yourself — and that’s with identical hardware.