other coins out there have their problem also, they are not perfect, their problems won't come off because they have no volume like bitcoin, we just need to reach the consensus to fix the known issue
And "consensus to fix the known issue" is essentially impossible, for exactly the same reason that protects the 21 million coin limit.
besides that if you start another chain you will have the same problem as now with the same consensus that will not be reached on the block limit etc..., what's the point?
Not all altcoins have hard block limits. But they will also run into problems. However "other coins running into problems" doesn't mean that bitcoin's problems can be solved. If you're falling out of an air plane, saying that others are falling too, will not avoid you crashing on the floor, right
The fact that bitcoin has a hard block size limit, makes that block chain space is a limited resource in the same way that the number of coins is a limited resource. From the moment that there's a market with finite price for that limited resource (like from the moment that bitcoin wasn't $0,- any more), the consensus mechanism protects this resource scarcity. As there is now a strongly rising fee for "room on the chain", this resource scarcity will be protected by the same mechanism that stops people form increasing the number of bitcoins beyond the original protocol.
Bitcoin having a fixed block size was programming, from the start, a scarce resource of "room on the block chain", that is coming to maturity. The artificial scarcity of coins, that made the market cap of bitcoin's coins, is now also applied to block chain room. Whenever this market cap becomes bigger than the coin market cap, and when "room on the chain" becomes a much more valuable commodity than (unmovable) coins, the 21 million coin limit will not matter any more, and the true value proposition of bitcoin will be "room on the chain".
This was baked in from the start in the protocol, by setting up a hard limit on block size.