Future proofing with mtb’s sounds like wishful thinking to me. I don’t know what budget your on. Mine is not much, at all, so I stay well back from the cutting edge.
I’ve got 456 evo with 4pot XTs and Hope/D521 wheels (both ancient), Z1 SL forks, 27 gears and a dropper that does nearly everything I need. I put the whole thing together for £350ish, it’s hard to work out as I had some bits, swapped others etc.
Yes my friends have full sus bikes that weigh less and are certainly more capable but the cost, the cost. Oh and I can usually keep up with them.
I also have a mini disc player..