Not always and not all problems are related to the quality of service provision.
If any troubles arise with the site, most owners immediately run to complain to the technical support service. But not always and not all problems are related to the quality of service provision. On the Internet, hosters often become victims of accusations that are not at all their responsibility. Often unfounded accusations spoil the reputation of good companies and lead to customer outflow.

Site unavailable
Even the highest quality hosting does not guarantee 100% availability of your resource 24/7/365. For example, the website king-servers.com indicates Uptime 99.9%, which allows unavailability for 1-2 minutes per day. Naturally, if you suspect that downtime exceeds the rate specified in the contract, you have the right to complain. And it is necessary to resolve this issue with the technical support service as quickly as possible. But first, use one of the services for checking real Uptime (for example, Yandex.Metrica) so that you have a serious reason to complain.

Website repair
This is absolutely not the responsibility of the provider, and if problems arise, you should contact the developer, not the hoster. However, it often happens that a freelance developer disappears in an unknown direction, and the customer does not have enough experience or money to hire a separate employee for administration and calls technical support. Here I would like to note that the technical support guys often step into the situation and help clients, if not with action, then with advice. But they are not obliged to do this and have the right to refuse.
Website hacking
A hosting provider cannot guarantee that a site will be protected from hacking, even if it really wanted to. It is impossible to prevent hacker attacks due to the fact that all common CMS, like other software products, are vulnerable:
They have their own weaknesses, which make it possible to upload malicious code that is well known to attackers. Keep in mind that today any website is hacked, even security service portals.
Excessive load on the server
Of course, high-quality hosting should ensure stable operation and correctly distribute equipment resources. But instability can also be caused by the developer himself. For example, a resource-intensive online order form in an online store may cause server failures when client load increases. And it is not the provider that limits your traffic, but heavy applications.
Before you complain, be sure to check whether you are causing the problem on your end.