Shouldn’t all guitars sound the same? Because if they don’t they’ll make different sound while playing with the band !
No, they shouldn't. In acoustic guitars, material and construction impact the tone, sometimes considerably. That doesn't mean they sound wildly different and incomparable - there are just some slight differences in the tone between models. And if the acoustic has a preamp system, differences in electronics impact the tone a lot.
If you tune two different guitars up the same they'll still be able to play the same notes, they'll just have a different tone. Kinda like if you're listening to a song and you mess with the EQ so it has more treble or more bass. An acoustic guitar will always sound like an acoustic guitar, but some will have a more pronounced low end, or crisper highs, or better sustain.
Even two of the same model often don't sound the same acoustically. This is due to things like physical differences in timber, neck angle and ageing effects. Between makes and models, things like type of timber and top thickness, air volume in the body, and top bracing patterns have a huge impact on tone