Focus on Rhythm, Not Harmony
I would suggest that the root of your issue is not harmonic, but rhythmic. Your post suggests that you're already in very good shape harmonically. It also seems like you probably have good technical control too. You've made good scale choices, you're already emphasizing the 1, 3, 5, and 7 of each chord, and you're using some passing tones (chromatic leading tones go a long way to make lines sound jazz-y). You're using pentatonic scales too, which can sound really nice when played immediately after/before scalars lines with chromatic passing tones.
So you're already doing things right, harmonically speaking. We can probably rule that out as the main problem, which leaves rhythm as a likely area to focus on. In fact, the issue you've described is extremely common among players who are technically proficient but new to jazz.
On guitar and piano, the challenge to play something rhythmically interesting is greater because nothing forces us to break up our phrases. By contrast, horn instruments have to think about phrasing, because they must stop playing every now and then to take a breath. But piano and guitar can play eighth notes ad nauseum with no pauses or rhythmic variations. It doesn't take long for this to stop sounding like jazz. Phrasing is really important in improvisation.
There are a lot of ways to introduce more rhythmic diversity into our playing. David Berkman told me once to choose a player who excels in this (he mentioned Kenny Kirkland) and transcribe & learn to play many their solos. One of the all-time greatest masters of this was Charlie Parker. And in general, you'll find a lot of interesting rhythmic variation in bebop music. The dotted quarter is a cornerstone of those rhythms. Transcribing full lines and phrases is ideal, but you can also try simply adding dotted quarter spacing between two notes. For example, if you play four eighth notes and end the phrase on the upbeat of 2, then you can start your next string of eighth notes on the downbeat of 3. Another technique--which is somewhat similar to the dotted quarter--is the use of a repeating 3-beat cross-rhythmic pattern. For example, here's four bars of bebop-style improvisation in F major:
The very first phrase is played first starting on beat 1, and then a second time starting on beat 4. We could repeat this lick a third time, starting on beat 2 of measure 2. This is a 3-beat lick, and repeating it a few times creates a nice cross rhythm to the 4/4 time. This rhythmic tension catches the ear. At the end of measure 3, we also see the dotted quarter spacing, which interrupts the eighth-note lick. The C on beat 3 is followed by a B♭ on the "and" of 4. This adds rhythmic variety, which makes the line rhythmically interesting and gives it a jazz-y/bebop-y feel.
Eighth Note Groupings & Accentings
As described above, we often hear bebop musicians achieving rhythmic variation through rests and/or variations in note duration. The dotted quarter is a quintessential note spacing. But there are other ways to create this rhythmic grouping, structure, diversity. Even if you're playing a long run of eighth notes, you can still create rhythmic emphasis by grouping notes a specific rhythmic pattern:
This is a Charlie Parker-esque lick, and you can hear something similar on his 1942 version of Cherokee at ~1:41. Every note has the same duration and there are no rests. But despite this, we still see a 3-beat, 3-beat, 2-beat rhythmic pattern. I've highlighted the first note in each grouping. The 3-3-2 pattern appears in the first two bars and again in the last two bars. The 3-beat group contains 6 quarter notes, and it effectively creates the same 3-beat cross rhythm discussed above. The accents contribute to this rhythmic pattern, emphasizing the first note in each group (among other things).
Beyond rhythm, there is one last element to the playing that can make your lines sound like jazz: the feel. We want the lines to swing. This doesn't necessary mean playing swung eighth notes. In a lesson, Gary Smulyan once told me that modern swing means playing straight eighths slightly behind the beat with a small accent on upbeats. Finding a good swing feel can go a long way to improving the sound of lines that are already harmonically interesting.