In text for our largest site is about 25% of our total earnings - very variable (by a factor of 10 some months) but overall a solid and significant part of our earnings.
Some time ago I realised that in-text ads were not suitable for mobiles and that was a downer with mobile views increasing all the time. Recently though they introduced "in-picture" ads and these perform well on mobile pages - very early days though.
"Swanny" persuaded me to give them a try many moons ago and I am many thousands of ús in his debt now because of the success of the ads.
Bottom line is that they work very well for some sites but are a total failure for others. Give them a try and see how they work for you.