Of course they don't force you to use spotify, but it's one of those "soft monopolies" many other companies have. It's not the only option, but they basically are, because everyone thinks so: it's like whatsapp, if you catch my drift (everyone use it because everyone's on it)
And when a company realizes they're in that position, they will prey down on their users without fail, and I'm talking about:
Privacy invasive app: https://reports.exodus-privacy.eu.org/en/reports/com.spotify.music/latest/
Investing in military AI: https://mixmag.net/read/spotify-daniel-ek-ai-defence-investment-criticism-news
Patents for extremely invasive technologies: https://www.accessnow.org/press-release/spotify-tech-emotion-manipulation/
Allowing disinformation during covid, not paying properly the artists and many other things I'm not going over for sake of brevity: https://en.wikipedia.org/wiki/Spotify#Criticism
What I don't like about spotify and all the companies who are in a similar position in the market is that, as usual, their share of the pie it's unfairly big, which is why I try to drive people away from them. Not saying YouTube is better, but at least with vimusic you don't have to listen to ads (which I think heavily harm people's mental health, among other things)
Of course music can be bought, but people only buy what they like nowdays, and use online services to discover new music. Few have the money to buy music and listen to it for the first time afterwards. Many people don't even have the money to meet their basic needs, let alone buy music