I am sure you guys see this too (everywhere)...
There may be several reasons why people keep saying bitcoin is the only blockchain project to survive. I'll list a few, perhaps you guys and gals can think of more?
1) They are in BTC from the beginning and have never really done any research after the first several blockchain projects came after btc (of which a lot failed yes).
2) They see altcoins only as a way to enlarge their ownership of BTC and need to occassional spreading of fud to make sure alts do not get too popular which could negatively impact bitcoin dominance...
3) They got in too late to the party, bought into btc only at ath and after the huge (and obvious/logical) drop they have all reasons to see btc get to ath again.
4) They are burned with one of the failed blockchain projects and got out completely or only support bitcoin.
5) They are anti-crypto and don't see any point in having crypto play a vital role in incentivizing blockchain (crowd funded) projects.
I am not talking about those that simply support BTC over any other project (which is fine and their choice), I am referring to those that will never pass up a chance to completely burn any other blockchain project to the ground over bitcoin.
Got any other reasons?
Not ruling out the fact that most Altcoins are SCAMs, but i bet they are wrong as i do not see BTC dominating for long. Altcoins with real world use case that are lucky to gain mass adoption are here to stay.