Is it worth it learning how to use 7400 series "jelly bean" logic IC's or are they completely obsolete?
Don't think for one minute that just because you have an FPGA that learning about 74xx is obsolete.
For designing with FPGA you must be able to 'see' the logic working in your head at a discrete gate level (you will learn this skill from discrete logic chips 74xx, cmos 40xx ).

Programming an FPGA is NOT like writing a computer program, it looks like it is, but only the idiots will tell you it is.

you will see many ,many people on the net talk about their FPGA design is big or slow, in reality they just don't understand how to think at a true multiprocessing parallel gate level and end up serial processing most of what they try to do, this is because they just crack open the design tools and start programming like they are writing  'C' or 'C++'


In the time it takes to compile a design for an FPGA on a home computer, you can breadboard a simple logic design in 74xx
Using FPGA for a design you MUST work with simulators rather than with the 'hard' FPGA
That is to say, if your 74xx design is malfunctioning you can fiddle with the connections, with an FPGA you must re-write, re-run a simulation, and then spend upwards of 30 minutes re-compiling the FPGA design.


Stick with the 74xx or 40xx range, build some 'adders', 'shifters', and LED flashers with gating, once you are used to seeing discrete chips it becomes easier when working with a massive 'blob' that is an FPGA