Comment by lmm

If it's taking you this much effort to do the trivial conjugations (seriously, the whole page barely mentions the interesting ones 80% of the way down, and falls back on "yeah, you just have to memorize the patterns" for た/て forms), yeah, just memorise them. Language learning and exercise are the two things where I've found the programmer's instinct to "work smarter, not harder" works against you; you actually just have to put the time and effort in.