But the west, without hindsight, seems to support their imperial ideology and strategic interests better. It seemed far more glorious to Seleucid kings to attempt to reunite Alexander's empire and style themselves in the mode of the glorious conqueror, than to chase steppe barbarians across endless stretches of grassland. The Seleucids also thought they could control it with careful usage of vassalage, tribute, and occasional military expeditions, while Ptolemaic Egypt threatened the core empire far earlier.
That is true, however it is not necessarily the case that the XXXIII Dynasty was seen even by the people at the time as the most prescient foe. Indeed, Seleucid policy required the usage of vassals and colonization efforts to maintain the frontier with the steppe. Seleucid rulers took the position as the guardians of civilization against the hordes of barbarians on all fronts, especially the north.
Meanwhile, as I take it, the Seleucids did not see the XXXIII Dynasty as someone that could truly destroy their realm. Rather, I take it, that they viewed the XXXIII Dynasty more as a weak foe, whom they could dominate simply with their demographic and territorial weight and hence integrate. Likewise, their interest in Italy, Greece and so forth was linked to a feeling that the Seleucids were the dominant Hellenic realm, able to enforce its hegemony with its massive size alone. However, such a massive size comes at a price and the Seleucids failed to correctly decipher their role. You cannot both be the protector of civilization and enemy of the steppe invaders (while they are strong and in a turbulent phase) and yet also seek adventurism into the west. At least, it is not advisable. If the Seleucids are not fell by the Dahae destroying their east, the Yuezhi will do so in short order. In otl, the Yuezhi were stronger than the Dahae and would be able to more critically smash the Seleucid state.
So as to the poster's question, had the Seleucids perhaps taken a more gregarious and diplomatic tone with west they could have done much better. For instance, using their protecting of civilization as a way to acquire tributes or simply as a way to receive some form of submission for others. All the while managing a colonization and policy of expansion in the east. The Seleucids can do this, they simply must find a more safe way to engage in their Alexandrine Legacy and in dealing with their immediate west.