This is an issue with my conlangs I'm tired of. Sentences tend to sound highly repetitive due to their regularity. In particular verbs almost always end in the same suffix, just because there's only one possible marker for tense.
I'm unsure how to mitigate this. I've tried replacing the tense markings with inflectional endings that also mark person and number and whatnot. But besides the fact that I don't really like that, it doesn't do much to mitigate the repetitiveness since the third person singular endings are always used disproportionately often.
Looking at natural languages hasn't really helped much. I've noticed that tense markings tend to be a single phoneme in European languages. This is obvious if you look at the third person singular form for verbs in English and Spanish. In English we use a -s suffix, in Spanish its an -a. And neither of these are unique to verbs. Spanish also uses singular phonemes to mark its imperfect tense. In English, we use the suffix -ed (which is often just pronounced as a 'd'), but a lot of English's more common verbs use stem changes or suppletive forms for the past tense. And then there's the case of Japanese. All verbs in Japanese end in -u for its non-past/infinitive form, but since Japanese is written with a syllabrary this means that verbs can end in almost any glyph that represents a syllable that ends with -u (though the syllable 'ru' is an abnormally common ending for verbs). Also, it has a number of different past-tense endings that depend on what the final syllable of the verb is (along with whether its classified as a 'vowel' verb or a 'consonant' verb). The only similarity between these endings is that they tend to end in -a and most incorporate alveolar consonants (I believe all of the possible endings are -ta, -tta, -nda, and -ita).
However, replicating this in my conlangs is difficult, probably because I tend to mark verbs for too many things. Pretty much all of my conlangs have absolute tense, aspect, and sometimes relative tense on top of this. I can't help but make regular, agglutinating endings for these, and the shear number of possible combinations would make an inflectional system impractical (one of my conlangs has hundreds of possible combinations of endings its verbs can take!)
Grammatical regularity can be such a rut at times...