What sort of instrumentation would be onboard? The last mission destined to leave our solar system was New Horizons[0] and its equipment was designed in the early/mid-2000s with the express goal of imaging the outer planets. Both Voyager probes have some instrumentation still sending data back to Earth[1] as well, though current projections estimate we may only be receiving data from them for until the end of the decade. Sending a probe out that only improves on a few areas such as ionized plasma detection and gas chromatography to determine what elements are in the heliosphere seem to arbitrary improvements on a short timeframe; but these are systems designed with a 50+ year lifespan. The 500 page report published by NASA[2] for a future insterstellar probe is a bit much for a layperson to understand, but such a program can also be done over a longer timeframe to justify its continued funding.

It's been over 40 years since we last launched a probe with the express purpose of exploring interstellar space, and technology has improved to the point of enabling these missions to be multi-generational by planning further launches to create a networked constellation. When I was a kid seeing the 'Pale Blue Dot' image in the book Cosmos, it gave a perspective of looking at humanity's achievements on a cosmic timescale instead rather than only the human timescale, and I think setting long-term goals of exploring our universe are held by everyone regardless of nationality. Delivering tangible results to the public like JWST's fantastic images and the 'Pale Blue Dot' photo are arguably just as important as the scientific data gathered.

[0] https://en.wikipedia.org/wiki/New_Horizons#Science_payload

[1] https://voyager.jpl.nasa.gov/mission/status/

[2] https://interstellarprobe.jhuapl.edu/Interstellar-Probe-MCR....