This will likely evolve to include extreme spectroscopy if any desire to detect an exoplanetary atmosphere is to be taken seriously, but that‘s possibly decades away even for professionals.
Professionals have been characterizing exoplanetary atmospheres for a number of years already! I’ve been doing voluntary work with the ExoMol team at University College London for the last couple of years specifically to help astronomers characterize the atmospheres of exoplanets and very cool stars.
I agree that current amateur equipment would find spectroscopy of atmospheres extremely challenging to say the least. On the other hand, radial velocity measurements may well be feasible, given that relatively inexpensive (circa 10,000 pounds/euros/dollars) spectrographs fitted to 0.5m class telescopes have already shown to be capable of measuring RVs to within 50 m/s — that typical of hot Jupiters orbiting close to the star, especially so if the star is a late M-type with a mass of around 0.3 M_sun.
Added in edit: @stellarplanet has Tweeted only today about the detection of CO, H20 and CH4 in exoplanetary atmospheres. Several posters at the conference were on the subject of exoplanetary atmospheres.