Choose a chord progression and practice soloing using only triads. Start with the basic triad of each chord (1-3-5). When you’re feeling comfortable playing only triads (or when you’re getting bored), start to mix in other ideas while still laying the focus on triads. You could use chromatic ornamentations to embellish the triad notes. Or you could start a phrase with a scale fragment and end it with a triad or vice versa.
After that, also practice soloing with every other diatonic triad separately.
After you practiced some or all diatonic triads by themselves, try combining them.