It’s difficult to make generalizations about hotels and hotel chains, and there are arguments for and against. Every city has a different best hotel, every chain has good hotels and bad hotels. On average, some chains are better than others.

I used to be a huge fan of boutiques and inactively avoided chains. But I found a lot of advantages that chains offer:
1) Boutiques tend to have poorer service. With a chain, there is some semblance of service levels that the brand *tries* to make consistent across all hotels. Every boutique is completely different from each other.
2) Lack of experience. When a chain opens a hotel, they’re leveraging decades of experience in putting this together and maintaining it. Boutiques often don’t have that advantage.
3) Boutiques rarely have all that I want in a hotel. Boutiques, on average, have fewer features. Ett Hem in Stockholm, for example, doesn’t have a swimming pool. I don’t think that’s a bad thing for them, but if you expect to stay at a hotel that has all the amenities, you will be disappointed.

Above is a generalization of course. I’ve stayed at boutiques that are out of this world. And I’ve stayed at chains that blow your mind. There are also hotels that are vice versa.

It’s worth mentioning that some specific chain properties were once themselves “boutiques” and acquired by said chain. And IME, they still tend to keep many of their unique traits. The Al Bustan, for instance, wasn’t always a Ritz (and locals don’t view it as a Ritz). The Crillon in Paris is now a Rosewood hotel, and if find that many people don’t realize it’s a Rosewood.