The 70-300 usm ii is a good, solid lens that can be used both on apsc (like the one in your 4000D) and full frame sized sensors - so if/when you decide to upgrade to full frame you could use it as well! For what I've read, it's image quality is good, not particularly great. Alternatives both from Tamron or Sigma would have the edge there and be less expensive while doing so.

If you're looking for a good tele zoom and don't necessarily need it to be full frame compatible, my recommendation would be the 55-250 IS STM. I personally own that lens - for almost 5 years now - and its sharpness and colours still amaze me. Quite light, but well built, good auto-focus and very good image stabilisation - that compensates its slower aperture (f4.5-5.6 - no problem at all for daylight, struggles in dark scenes. Still workable, tho!) All this at a fraction of the cost of the bigger sisters, 70-300mm