If you are a handy person, hanging your pieces on a frame is not that hard.
I started road biking in 2017 and after getting to know a bike shop guy (independent shop) he suggested me to get an steel bike.
I found a nice one with down-tube shifters at the beginning of 2018 and had fun getting all the hardware to put on the frame.
Removed all the old pieces myself, did cold setting, touched the paint, cleaned the headset, aligned the drop hanger, treated inside the frame, etc.
But since didn't have any experience and wanted the bike set up, asked the bike shop to put it together with the new pieces.
Fast forward, I put together 5 bikes since.replacing the comps to different ones.
The main thing is the initial investment on required tools - you will need tools for old components as well for the new ones if you are going with brifters and 11 speed cassetes.
Also, gave it a try to build a set of wheels that is still good after some 4 k miles
Have fun!