If startups never entered markets with competition, we wouldn't have Google (Altavista was market leader), Lyft (Uber), Zoom (Microsoft/Skype) or countless other darlings that are now large publicly traded companies... It's more important to choose a market where you feel that you have a competitive advantage over incumbents. Could be tweak to their product that you believe adds additional value, could be the strength of your team and your ability to move more quickly, could be your go to market strategy; the key is finding something that separates your brand from others in the space and carves out a piece of the market where you can be successful. There is always room for innovation in any market, even those that are fairly saturated with competition. Find your competitive advantage and exploit it!

Hi
You’re correct: it is indeed very difficult to create an entirely new service or product, as almost ‘everything’ has already been invented.
That said, 2 points to consider:
1. Sometimes small changes to existing services or products can make a huge difference (and fulfill a different need for potential consumers). For example, Airbnb (hotels existed, rental units existed... - they just added a twist).
2. Existing competition isn’t necessary a bad thing. If you are selling an entirely new concept, you need to ‘Educate’ your potential costumers - this is both extremely expensive and often very difficult (and timely) to do. Many companies have failed just because they were before their time, only to see other companies succeed with similar products a few years later.
The bottom line is this: although it’s important to research your competitors and to make sure that the market isn’t saturated, the only sensible way to know if there is (enough) need, is to validate your idea (see my past answers for an elaborate explanation on how to do this).
I’ve successfully helped over 300 entrepreneurs and I’d be happy to help you if needed.
Good luck

The short answer is yes! And the key to success is to add value - give the customer something extra that makes you distinctive. For example, when my car is due for its MOT, the garage picks her up and brings her back cleaned inside and out for no extra cost.
The fact that companies are already servicing the market is encouraging. However, don't stint on your research - is it a mature market about to decline or a robust one able to sustain more supply? Is it an embryonic market, ripe for new entrants? It's quite possibly somewhere in the middle. Whatever, talk to customers (potential or those of existing suppliers) and find out what their needs are and especially the ones that are not being met.

Differentiation is the key. Absolutely yes if you can offer some kind of differentiation to the customers (extra added value, added services, features...)

Depends on the sector, category if its B2B or B2C, normally in a B2B space there will be always an existence of multiple players and market will be fragmented.
B2C space is where you need to be a little careful & ensure you move fast enough and have a differentiation with a plan to build that.