Adobe should sell InDesign software outright.

That ship sailed a long, long time ago. More and more companies are going to a subscription-based fee. They're not going back, either.

Here's an article I wrote 6 years ago. Beyond the subscription numbers listed which have ballooned to millions of users, nothing in there has changed.

https://www.boblevine.us/why-creative-cloud-subscription-software-is-here-to-stay/

Unfortunately, this is not an avenue to contact Adobe - you can put your voice across here https://indesign.uservoice.com/ - and these are monitored and checked and replied to - the more people you get on board to vote for your idea the better, but it's not the main reason Adobe listens to users - you don't need a lot of votes for them to listen - just a reasonable request will do.

In terms of other applications that suit your budget:

Quark is a one off payment and a perpetual license - so you don't need to keep buying it with options to upgrade at later points.

Affinity is the same and a very cheap one-off payment 

Scribus is an open-source similar to InDesign

There are others if you look for them.

In terms of InDesign - it's payment model is currently subscription-based. 

Your options are relatively simple:

Commit to an annual plan and pay monthly for €24.59/mo

OR

Standalone Monthly Plan for €36.89/mo (needs to be renewed on month-month basis)

OR

Annual Plan and pay a 1 off fee for the year for €294.97 / year

And to be honest sounds reasonably priced to me.

That plan (skipping upgrades) worked for your budget but didn’t work nearly so well for Adobe’s budget. This is the new world. (Not an official reply). 

If you only use InDesign occasionally, you can pay a little more and subscribe by just the months you want to use it.

You might look at other solutions from Affinity or other vendors if you feel that strongly. The Adobe train left a long time ago.

While it may not work well for you, it does for a very large number of people (and companies), and Adobe is doing very well using the subscription model (check the stock market).