Depends on what you expect of them. Trendlines, if drawn correctly, will tell you whether or not a trend is in place, what its direction is, what its strength is. Once plotted, a TL, like a moving average (which is a moving trendline), will tell you whether or not momentum is slowing and alert you to possible trend change and trend reversal. In your example, a new TL is drawn when price makes a new low. When that line is eventually broken, there is likely a change in direction, in this case from downward to sideways (price can also resume its downward movement, perhaps even dropping again below the TL). When the last reaction high (the red arrow) is exceeded, there is likely a trend reversal. In this case, price dropped back below the last reaction high, casting doubt on the reversal. If nothing else, the reversal was to take months longer, which is not unusual with rounding bottoms. Now we're attempting another reversal. Whether or not it succeeds, however, is still an open question.
Prox, Where did you get the road map posted above ? I've seen some of your charts before and they were surely not like that one
Draw an axis of symmetry between FEB and MAR words. Butterfly it over so you can see the "saucer" formation you are charting.