Its not inconsisant at all to say that too many chumras lead poeople over the edge, It clearly says you are not to veer from the torah from the left or the RIGHT
If you think that means that it is assur to do chumras, you are very mistaken. The gemara is full of chumras that it discusses amoraim doing, and does so with admiration usually. (with exceptions like Rabi Tarfon who did like Beis Shammai)
Why just in a few day’s ago’s daf we had the story of the tannaim on the boat who were machmir against the halacha for techum shabbos.