I think the purpose of all altcoins in crypto is to be an alternative investment to bitcoin itself, as we know bitcoin
created in very limited quantities and the value is very high, therefore altcoins are an option other than bitcoin for investment, but we also need to know that the price of altcoins is very dependent on bitcoin development, if btc goes up altcoins will also increase, as well as otherwise,
Like I said, it is a free choice and bitcoin is not forced upon someone to be the only "alternative" to fiat currencies but there are options elsewhere too.
The difference in opinion is there and expressing it is possible too and shown in an healthy manner in this as an example. With bitcoin on the toplist, it does receive hate from the owners and bagholders of altcoins, but we all know that the biggest source of money to spend on altcoins is through bitcoin and not fiat and therefore the price movements.
if you want to collect altcoins then you can say that Dogecoin and Shiba inu are memecoins that have no purpose. but for me in cryptocurency only to seek profit from various types of altcoins, which have the potential and trend of altcoins in the future.
They can have a purpose if they are used for something else other than just a mode of payment which can be true for any coin. That is why the developers of these coins attempt to bring in some merchant contacts into their their system in order to market the demand of their coin.