When it first started, Bitcoin was created as a means of disrupting the corrupted financial architecture. The idea was that Bitcoin would be used as a future currency of people that is fast, private, and cheap. Unfortunately, it soon became apparent that centralized exchanges were not safe, and that it was too expensive and slow to transact in Bitcoin.
With the market success of Bitcoin, several other altcoins sought to enter the market. They started entering the market on the basis that Bitcoin was not private, fast, or cheap enough to constitute a new form of currency for the entire world population.
Initially, these alternative currencies had a point. The Bitcoin price was the highest, but it still had issues to address. Privacy-based coins such as DASH and Monero were introduced with inherent privacy features. Ripple was created to settle huge transactions between traditional financial institutions quickly, cheaply, and securely. Bitcoin Cash was forked from BTC for scalability reasons and was initially far cheaper and faster than Bitcoin. However, as Bitcoin evolves, it seems that most of these altcoins no longer serve a true purpose.
With the implementation of the Bitcoin Lightning Network, all the scalability issues of Bitcoin have been resolved. It can expand to easily adapt an almost unlimited number of users. However, as with all scaling systems, it will take time to grow organically. If too many users join a network in a short space of time, it will lead to problems for any network, even outside the sphere of the crypto market. The Lightning Network is essentially a sidechain of the Bitcoin blockchain, where transactions can be recorded without placing undue stress on the core network/blockchain.
Yet aside from this, there have been a host of resolutions. Regarding privacy, it is now easy to send Bitcoin transactions to a fake address where the cryptocurrency is effectively ‘laundered’ before reaching its host destination. In this way, the government and other nefarious actors cannot track your transactions. The Taproot/Schorr upgrade is also going to add additional privacy features, as well as reduce overall transaction costs. Bulletproofs and Dandelion are other privacy proposals in the work. This reduces the need for privacy-based coins such as DASH and Monero.
The most cited criticism of Bitcoin is that the technology is slow. This criticism is a little overblown, and it stemmed from a time back in 2017 when it took too long to confirm transactions due to increased interest.
But still, with the core blockchain network considered, Bitcoin is as slow as it was used to be earlier. It takes too long to process the transactions, which must be done within minutes soon after a BTC is sent from one wallet address to another.
The Lightning Network will function as a kind of credit network where transactions would be done immediately. Until it is fully implemented, high-speed altcoins have a reason to stay in the game, such as Nano and Futurepia. After implementation, most of them will be needless, and we will see a consolidation in the market. Cryptocurrencies that address a real need and possess their own use cases (IOTA, Ethereum) will remain relevant.