Let's look at the development of dukedoms (in the UK, not necessarily UK-dukedoms - also includes English, Scottish and Irish) - including only those that are still 'active' (several others no longer exist but were created):
1398: Rothesay (royal)
1460: Cornwall (royal - with 'breaks')
1483: Norfolk
(3 in total)
1643: Hamilton
1643: Brandon
1660: Somerset
1663: Buccleuch (royal: illegitimate son)
1675: Grafton (royal: illegitimate son)
1675: Richmond (royal: illegitimate son)
1675: Lennox (royal: illegitimate son)
1682: Beaufort
1684: Queensberry
1684: St Albans (royal: illegitimate son)
1694: Bedford
1694: Devonshire
(+12 = 15; increase of 400%)
1701: Argyll
1702: Marlborough
1703: Atholl
1703: Rutland
1707: Montrose
1707: Roxburghe
1719: Manchester
1766: Leinster
1766: Northumberland
(+9 = 23: increase of 60%)
1814: Wellington
1833: Sutherland
1868: Abercorn
1874: Westminster
1876: Gordon
1889: Fife (royal-related: husband of granddaughter)
(+6 = 29: increase of 26%)
1928: Gloucester (royal: son)
1934: Kent (royal: son)
1947: Edinburgh (royal: husband of daughter)
1986: York (royal: son)
(+4 (of which one will merge with the crown) = 33; increase of 14%)
2011: Cambridge (royal: grandson by heir)
2018: Sussex (royal: grandson by heir)
(so far: +2 (of which one will merge with the crown) = 35; increase of 6%)
So, since 1600 each century in the increase in both absolute and relative number has been lower than the previous century. (Again, the numbers are somewhat flawed as only the current active dukedoms are included but the pattern would be even more clear if we add the ones that are now dormant or no longer exist)
Nonetheless, it might make sense to discontinue the practice of giving dukedoms from the next generation onwards (I would still like to see Edward be granted the title of Duke of Edinburgh as he was promised and according to both his parents' wishes) and move to earldoms instead - if they decide to start giving peerages to both sons and daughters of the monarch. That would be somewhat consistent with the practice of giving earldoms to husbands of princesses - and might be an adjustment that would fit better with the times. In that way their eldest son would still be a Lord, the daughters ladies and other sons 'the Hon.'.
N.B. In the scenario above they could make Louis HRH The Earl of Cambridge (if his father by that point has ascended the throne). There have been previous Earls of Cambridge and it would be a nice way to continue the 'Cambridge' title in the family. And Charlotte could, for example be made 'Countess of Strathearn' (or the other way around of course) - continuing the use of her parents' Scottish title.
No need to give husband’s Earldoms. It’s a tricky one because what move could still be seen as potentially pragmatic. If husbands don’t get titles why should wives. Is that only because of the traditional form of women taking husbands names? You can’t win with it but there is a more manageable way of doing it then now. And like it or lump it it should start with the Sussexes and with the family or not I feel it was always going to be the thing when Charles becomes King.